# Choices for kid-sized Crank Sets



## antonio (Jan 18, 2005)

I just scored a nice little Craigslist find for my 11 year old daughter - a 2006 Stumpjumper Women's, size 13.5" .

Overall it fits her very well (I switched out and flipped the stem, replaced the front tire, and will swap the saddle soon). However, the cranks are 170mm. I know there are a few sources for shortened cranksets, as that info is scattered among multiple threads, but I am wondering if you knowledgable folks would mind consolidating them into this one thread. Thanks!

As pic'd, 24.3 pounds.


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## wpgbike (Jan 6, 2015)

Trailcraft has 152 mm cranks for $80. I got them for my sons bikes, they seem fine so far.


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## CJH (Apr 21, 2004)

Is there enough material on the current cranks to have them drilled and tapped to the length you want?

There are places you can send your cranks to do this. Others have bought the bits and had local machine shops do them. And there is the DIY option.


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## antonio (Jan 18, 2005)

wpgbike said:


> Trailcraft has 152 mm cranks for $80. I got them for my sons bikes, they seem fine so far.


Thanks. Those seem to be a popular choice which I'm strongly considering. Glad to hear they're working out for your boys.


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## antonio (Jan 18, 2005)

CJH said:


> Is there enough material on the current cranks to have them drilled and tapped to the length you want?
> 
> There are places you can send your cranks to do this. Others have bought the bits and had local machine shops do them. And there is the DIY option.


I never even knew this was an option, Thanks! Seems like I have a little bit of research to do.


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## SAAZ (Dec 29, 2009)

I bought the Trail Craft crankset for my daughter's bike. They are a very nice 2X crank. I also bought a 152 mm crankset off ebay (Spectra branded) for another bike. It was surprisingly nice. I set it up for a 1 x 9 on my other daughter's bike. I think that was $28 with $14 shipping.


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## RMCDan (Feb 28, 2008)

If you need to go shorter than the Trailcraft cranks and it's a square taper BB, some options include:

-SINZ makes BMX cranks down to 115 mm. Only available in a 5-arm 110 BCD spider though. You can find them on BMX websites.

-Spawn sells 127 mm cranks with a standard 104 BCD spider
Alloy Cranks ? 127MM - Born to Ride | The World's Best Kids Bikes!

-I found this website in Holland that sells a bunch of short steel cranks (85, 102, 115, 127 and 152 mm options) with fixed chainrings. 
https://en.hollandbikeshop.com/bicycle-parts-children-s-bikes/children-s-crankset/

edit: The Holland Bike Shop cranks turned out to be steel, not aluminum as I was told. Thankfully they fully refunded me (including shipping).


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## ProjectMayhem (Aug 23, 2013)

Pair Thorn triple Solo Alloy crankset 110/74 pcd - £69.99

Thorn do 140 145 and 152 (iirc) not sure if they are available outside uk.


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## CJH (Apr 21, 2004)

antonio said:


> I never even knew this was an option, Thanks! Seems like I have a little bit of research to do.


There is an online article out there somewhere that not only discusses this but also lists cranks that are good candidates. If I find it I'll post it back here.


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## dc40 (Oct 4, 2013)

Lil shredder is getting into the market too. Not sure if available to the public yet. They had some on their FB page a few months back.

You can checkout Bike Smith Design for shorting cranks:
Short Bicycle Cranks


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## GrayJay (May 16, 2011)

Recent thread with my DIY crank shortening pictures and description at:
http://forums.mtbr.com/families-riding-kids/sx-26-trek-4500-kid-build-961774.html

Minimum amount that a crank can be shortened is around 20mm, probably best to find a set of ubiquitous used 175mm MTB cranks if you want to shorten, save the 170mm set a couple of years for her to grow into. (it will not take long!)

I you cannot borrow a set of R&L 9/16" thread taps (or a LBS shop that will tap the new holes for cheap and or you are not planning to have a dozen kids), then it probably makes more sense just to buy the pinecraft cranks rather than DIY or trying to pay someone do shorten them for you.


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## boomforeal (Nov 9, 2005)

SAAZ said:


> I also bought a 152 mm crankset off ebay (Spectra branded) for another bike. It was surprisingly nice. I set it up for a 1 x 9 on my other daughter's bike. I think that was $28 with $14 shipping.


what was the bcd on those? they look like a decent, affordable option, hoping they take 104mm chainrings


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## SAAZ (Dec 29, 2009)

Yep, they do take 104mm chainrings. I'm actually really pleased with how nice they are.


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## antonio (Jan 18, 2005)

I will likely give the Spectra a try. 

SAAZ, what bb did you use? What was the spindle length? Thanks.


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## SAAZ (Dec 29, 2009)

I used a Shimano UN55 square taper, 68 x 113. Fit perfectly. Not the lightest thing in the world.


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## TigWorld (Feb 8, 2010)

I've got a list of short cranks that I've been maintaining over the years here. I've also shortened a number of sets of cranks and its a good way to go to get the exact size you need.


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## Fargo1 (Oct 19, 2012)

SAAZ said:


> I also bought a 152 mm crankset off ebay (Spectra branded) for another bike. It was surprisingly nice. I set it up for a 1 x 9 on my other daughter's bike. I think that was $28 with $14 shipping.


Is the chainring on that riveted or screwed on. Can it be replaced with different chainrings or a bash guard? I'm looking at it for my sons bike.


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## Fargo1 (Oct 19, 2012)

Well I just ordered this crank. I saw 2 sold in the hour before and just decided to give it a try. Which one of you ordered 2 of them?


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## lixxfe (Apr 19, 2012)

*Turn 3 Racing*

https://www.facebook.com/turn3racing 
BMX News Product Review - Turn3 Racing Cranks


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## SAAZ (Dec 29, 2009)

Fargo1 said:


> Is the chainring on that riveted or screwed on. Can it be replaced with different chainrings or a bash guard? I'm looking at it for my sons bike.


It is bolted on...a standard 104 bcd pattern so there are quite a few chainrings available as well as bashguards. I have a 32 tooth ring on there now. I'm thinking about trying a race face 30 tooth.


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## ETChipotle (Sep 20, 2014)

I have two of the Spectra cranks, the first one I've installed a 30T Raceface narrow-wide, and it also has the smaller BCD if you wanted to go with a sub-30T chain ring. I used the chain ring bolts that were holding on the original Spectra chain rings. The second one I plan to use soon, and was going to go with 32 on that one. Both going on Hotrock 24" bikes. The first one was an incomplete bike I got at my LBS, and I put Ace 20 rims on XT disk hubs, and I'm lazy so I only put half the spokes on. It's 9-speed 11-34. My youngest daughter loves the bike. The other one will be 10 speed 11-36 with the rear wheel being an Ace-20 laced to a Circus Monkey purple anodized to match the bike. No plans to re-build the front wheel.

I didn't know what size BB to get, and with the 113mm Shimano square taper it looks like I could use a spacer to improve the chain line. No hurry though, she doesn't shift out of low gear.

The 30T and 32T might be too low for them in a few years, but those would be good things to have in the parts bin.

I have a little postal scale somewhere, I'll weigh the Spectra arms I haven't used yet if somebody else doesn't get to it first.

I was trying to figure out what the Spectra brand is, and all I can tell is it may have been part of the Bianchi group. Not my area of expertise.


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## Fargo1 (Oct 19, 2012)

Thanks for the info guys. Glad to get confirmation the rings are bolt on. That is what I thought they were from the pictures. 

I'm getting excited about these cranks. Everything you guys say is sounding great. ETChipotle I'd love to hear what they weigh out at for you. The info on the ebay page says "531g + 219g (750g)" I was a bit confused what the 2 weights were for. I assumed crank at 531 and steel chainrings at 219. So I've been toying with going to a aluminum 30t 1x8 setup. I figured that could really same some weight.


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## TigWorld (Feb 8, 2010)

Weights are probably right side crank arm (with rings etc) and left side crank arm.


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## CJH (Apr 21, 2004)

TigWorld said:


> I've got a list of short cranks that I've been maintaining over the years here. I've also shortened a number of sets of cranks and its a good way to go to get the exact size you need.


That's the article I've been looking for.

Do you have an opinion on crank length for kids? My son's Superfly 20 has 145 mm cranks and his inseam is only 20.5". He has a long torso and short legs, evidently, so the bike fits him fine but it's clear the cranks are too long.

Want to swap them out before his first triathlon next month.

I'm torn between the Spawn 102mm and 127mm cranks.


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## Red Rock (Sep 12, 2014)

My son's inseam is 18.5 inches and he is riding 127mm cranks comfortably.


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## Surfpoodi (Sep 14, 2011)

My son's inseam is 22"ish and he seems good with his 140mm cranks.

He had been using 125mm cranks until a few weeks ago with no issues


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## RMCDan (Feb 28, 2008)

CJH said:


> I'm torn between the Spawn 102mm and 127mm cranks.


127's for sure. 102 is probably too short, and the biggest chainring you can put on that 64 BCD spider is 30t.


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## Cinq (Jan 2, 2003)

My 8 year old rides with 130 mm Sinz cranks and is very happy with them. The cranks are 5 arm 110 mm BCD. I have a 34 tooth chainring and a Race Face bash guard on them. He is 1m25 tall (49 inch and a bit).



















Kind regards,

Clemens


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## ladljon (Nov 30, 2011)

Ok, I have a 28-29" inseam. Last year I shorten my cranks. Wished I had known this thirty years ago...could have won more races....Now I'm riding 125mm on the road bike and 135mm on the CX and MTB bikes. So, so much better....Breathe better, spin faster, or push a harder gear...


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## othello (Apr 10, 2012)

Have a look at this thread I created a while back http://forums.mtbr.com/families-rid...you-might-interested-906854.html#post11110874


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## joeadnan (Oct 21, 2003)

ladljon said:


> Ok, I have a 28-29" inseam. Last year I shorten my cranks. Wished I had known this thirty years ago...could have won more races....Now I'm riding 125mm on the road bike and 135mm on the CX and MTB bikes. So, so much better....Breathe better, spin faster, or push a harder gear...


Show us more of that BTC-equipped mtb. Looks like it has a custom anodized Rohloff.


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## ladljon (Nov 30, 2011)

MTB and CX with Rohloff...


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## dcp_nz (Apr 16, 2009)

ETChipotle said:


> I have a little postal scale somewhere, I'll weigh the Spectra arms I haven't used yet if somebody else doesn't get to it first.


ETC or anyone else have an actual weight on the Spectra Crankset?
It looks interesting - half the price of trailcraft or lasco and probably very similar weightwise when accounting for steel vs alloy rings.

If possible would love to know actual crank weights plus separate ring weights.

If the 750g is somewhat accurate I'm assuming I'd be down to 650-670 just by pulling the outer ring and with 104 BCD could possibly go 1x drivetrain with a 30 or 32 middle ring and be at around 580g for crankset plus additional saving from no shifter and derailleur.


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## Fargo1 (Oct 19, 2012)

I got my cranks a couple weeks ago and haven't put them on yet. I'll try to weigh them before I do. I did notice on one of the crank arms that it says Prowheel on it. That is the same company that made the OEM cranks on my kids Raleigh Mt Scout. Its a very different crank though, but it gives some insight into the company who makes them for Spectra.


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## Fargo1 (Oct 19, 2012)

I put the Specter cranks on my kids bike tonight. Using my wifes cooking scale the left arm weighed 218g and the right arm with the rings weighed 531g. Together both arms weighed 750g. Which was 100g lighter than the factory cranks. However, the factory arm was actually lighter than the Spector arm, so all the wight savings came from the rings. The big ring on the Spector is actually aluminum and the 2 smaller rings are steel. 

I did notice that the rings are offset quite different on the Spector though. My chain line is now way off. So I'm not sure what to do. I might just grind off the outside ring and make it a chain guard and make it a 2x. Since its aluminum (I checked with a magnet) it should grind down pretty quickly and not rust. If I knew what I was doing there is probably a way to adjust the bottom bracket too. I never touched the BB. Both bikes had the same square taper crank so I just took the factory off and put on the Specter.


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## jestep (Jul 23, 2004)

Not trying to dig up overly-old threads, but found these when trying to find some lighter weight components for my daughter's bike: Trailcraft Cycles

_Edit.. NM, missed the reference to these cranks in the first post. ^ Here's the link to them though..._

2x in the front at under 650g. About the best I've seen and the price is good. They also offer a 24" titanium fork at 660g but it's way on the high price end, at $400. Kid better be an active racer to even remotely justify that cost IMO.

I ended up going the Spectra route before I found these cranks. Running the spectra's in a 2x up front, with a 36 tooth equivalent race face light bash guard in place of the large ring. Comes in at under 700g and cost about $60 total. Still trying to find a cheap Ti or other lighter BB but this is still a vast improvement over every OEM crank I've found on youth bikes.


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## jh_on_the_cape (Jan 12, 2004)

Can anyone direct me towards square taper 94 BCD five arm short cranks?


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## backinmysaddle (Jul 27, 2011)

I have a 20" bike for my son and it has 114mm cranks with a fixed 32t ring (very light setup, just not ideal gearing). I would like to find either a 114mm or 127m crank that will take a 28t chain ring. Given how small the 20" wheel is, I'm getting pretty close to the ground with the rear derailleur as I increase the size of the cassette. I'm currently at 32t and at most think I can put a 34t on, so I really need to get a smaller front chain ring on. Any sources for 114-127mm cranks that will take a 28t?


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## TigWorld (Feb 8, 2010)

jh_on_the_cape said:


> Can anyone direct me towards square taper 94 BCD five arm short cranks?


I have never seen any commercially for sale. I did make a set of short cranks from some old LX cranks with 94BCD.


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## Surfpoodi (Sep 14, 2011)

Are you sure you need such a small front ring? A 32 ring to 32 rear on a 20" wheel sounds like a pretty low gear for a young kid. unless you are doing really big climbs... My son ran a 35 ring to 34 rear for years and it worked well for us. Albeit we didn't do huge climbs or anything, but he was only 4-6 years old.

But I guess if your son is older and looking to do longer climbs, then I can get my head around wanting a 28 up front.


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## lixxfe (Apr 19, 2012)

jh_on_the_cape said:


> Can anyone direct me towards square taper 94 BCD five arm short cranks?


Turn3 racing has some. Not cheap though.

Product Spotlight: Turn3 Racing cranks for the Micro Riders | bmxultra.com

https://www.facebook.com/turn3racing


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## backinmysaddle (Jul 27, 2011)

Still struggling here. Definitely need 28t for the climbs we do. I have 24t front 42t rear, and use it a lot ;-)

Bottom line is that virtually all of the short cranks I find are 110BCD and so cannot go small on the chain ring.

I found this triplelizer thingy that adds a 74 BCD ring to any 110BCD double. Possible I could use that on a set of 110BCD cranks as a "doublelizer" but I really only want one ring. Anyone seen a 110BCD rockring that includes mounting for 74 or 64 BCD chain ring? That or just an outright reducer from 110BCD to 74/64BCD? I have be sending this problem to a local machine shop...


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## silvascape (Sep 11, 2014)

Maybe you should check the roll out that the options you are looking at gives. Dont forget that a 24:42 on a 26" is about a third less roll out on a 20" wheel. This means a easy gear ratio on an adult bike is a super, super easy gear on a small wheeled childs bike. They are also hauling way less weight up hill. Kids have less strength and less leverage due to crank length but be careful assuming they need as low or lower gearing than adults as you also need to consider that their bikes have lower roll out lengths.

eg: bmx example - on my 24" bmx I ride a 39:17 gear with 175 mm cranks
my six year old on 20" wheels rides 36:15 with 125mm cranks. Just on gear numbers he is on a harder gear than me but take into account the wheel size and he is on a easier gear (not by heaps though and he spins this gear like crazy).


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## backinmysaddle (Jul 27, 2011)

I've used Sheldon Brown's online calculator, using "Gain Ratio" which he suggests is the only measure that takes into account crank length. I was surprised too, my off the cuff thinking when I bought the bike was that 32/32 would be fine. I put a 38t rear on and even 32t front/ 38t rear isnt enough granny for the steeps. I definitely need something smaller than 32t on the front. I am increasingly coming to realize i will likely have to use one of the 3x options and just keep it on the granny. Who knows, I may fit a front derailleur on later...



silvascape said:


> Maybe you should check the roll out that the options you are looking at gives. Dont forget that a 24:42 on a 26" is about a third less roll out on a 20" wheel. This means a easy gear ratio on an adult bike is a super, super easy gear on a small wheeled childs bike. They are also hauling way less weight up hill. Kids have less strength and less leverage due to crank length but be careful assuming they need as low or lower gearing than adults as you also need to consider that their bikes have lower roll out lengths.
> 
> eg: bmx example - on my 24" bmx I ride a 39:17 gear with 175 mm cranks
> my six year old on 20" wheels rides 36:15 with 125mm cranks. Just on gear numbers he is on a harder gear than me but take into account the wheel size and he is on a easier gear (not by heaps though and he spins this gear like crazy).


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## lixxfe (Apr 19, 2012)

backinmysaddle said:


> Still struggling here. Definitely need 28t for the climbs we do. I have 24t front 42t rear, and use it a lot ;-)
> ... I have be sending this problem to a local machine shop...


If you are willing to get some machine work done, the Spawn 127mm cranks, while intended for 104mm chainrings, have undrilled bosses where a 64mm chainring would bolt on to.

If you don't mind spending the money on Turn 3 cranks, I believe they have a 64mm spider available. If not, PM me. I have a spare spider that fits their cranks.


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## jestep (Jul 23, 2004)

Here's the weight breakdown on the spectras in case anyone wants them. This is with everything disassembled.

Drive arm: 298g
Other arm: 218g
Outer ring (Al): 80g
Middle (steel): 84g
Inner (steel): 38g
Outer bolts and retaining nuts: 18g
Inner bolts: 16g

~750g total. Can easily get this under 700g for 1x running a light bash guard and removing the inner ring, or if you went to Al middle and inner rings it would still come out under 700g.


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## backinmysaddle (Jul 27, 2011)

I found that Islabikes actually have a 28t chain ring on 140mm cranks for their Creig hardtail model
I couldnt get their US distributor to answer any questions about this crank and if it is available for order, so I contacted the UK office and hopefully they can hook me up with one. 28t front and 38t rear should be pretty close to what we need.


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## Surfpoodi (Sep 14, 2011)

One other direction to consider.... What about getting a OneUp or Wolftooth 42 cog instead? Then you could keep your current cranks with the 32 ring, and still get a pretty darn low gear. Seems like it could be more cost effective, and potentially reusable on future builds, rather than hunting a unicorn crank?

Just a thought.


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## backinmysaddle (Jul 27, 2011)

I'd thought about that, but the rear derailleur pulley will be way too close to the ground with a 20" wheel. 38t is about the max you can safely go with a 20" wheel. This is doable with a 24" wheel for sure though.



Surfpoodi said:


> One other direction to consider.... What about getting a OneUp or Wolftooth 42 cog instead? Then you could keep your current cranks with the 32 ring, and still get a pretty darn low gear. Seems like it could be more cost effective, and potentially reusable on future builds, rather than hunting a unicorn crank?
> 
> Just a thought.


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## GSJ1973 (May 8, 2011)

backinmysaddle said:


> I'd thought about that, but the rear derailleur pulley will be way too close to the ground with a 20" wheel. 38t is about the max you can safely go with a 20" wheel. This is doable with a 24" wheel for sure though.


What about a Shimano mid-cage derailleur with a longer b-tension screw and 42 tooth cog with 30 tooth narrow-wide ring?


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## backinmysaddle (Jul 27, 2011)

Wow, what a PITA this has been. I was also working on my daughter's 24" bike as well (also came stock 32x32 as granny).

For both, it was a snap to add a 38t rear cog, but moving to 42t was out of the question on the 20" (regardless of derailleur I tried, it dropped the pulley wheel to the ground). And for the 24" bike, I had clearance, but it was going to require too many parts changes to make sense. The 38t slides on and works with the existing 8 speed derailleur/shifters/casettes. The 42t wasn't working well, I think it requires moving to 9 or 10 speed stuff to really work well. So I scratched that.

So for my daughter I decided to get the Origin8 145mm crankarms, it's a 130/74 BCD triple set up ($48), then add an Origin8 26t chain ring for the 74 BCD mount ($20) and a 42t 130 bash guard to give it a finished look ($25). With the 38t rear and 26t front, she should be fine. And as she progresses I figure I can add a second chain ring and front derailler if she ever needs that. 

Now to figure out the equivalent solution for the 20" bike, which is even hard given how few cranks there are in the 114mm-125mm range that I would like. I'm convinced there are no single chain ring options and it will be another triple crank/ bash ring type solution. Again, hoping to keep it under $100.


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## joe_bloe (Nov 18, 2010)

My son loves his Lasco 152mm cranks from Utah Trikes. They're square taper triple cranks, we run them as a 2x with great results. Utah Trikes - Lasco 44/32/22 Triple Crankset 152mm w/Chainring Guard


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## Feldybikes (Feb 17, 2004)

backinmysaddle said:


> Wow, what a PITA this has been. I was also working on my daughter's 24" bike as well (also came stock 32x32 as granny).
> 
> For both, it was a snap to add a 38t rear cog, but moving to 42t was out of the question on the 20" (regardless of derailleur I tried, it dropped the pulley wheel to the ground). And for the 24" bike, I had clearance, but it was going to require too many parts changes to make sense. The 38t slides on and works with the existing 8 speed derailleur/shifters/casettes. The 42t wasn't working well, I think it requires moving to 9 or 10 speed stuff to really work well. So I scratched that.
> 
> ...


127mm cranks, a good length for 20" bikes, are easy to find on the Spawn site.

Alloy Cranks ? 127MM - Born to Ride | The World's Best Kids Bikes!

$60CAN ended up about $60USD including shipping with the currently US-favorable conversion rate.


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## backinmysaddle (Jul 27, 2011)

But those Spawn ones come with 32t ring which is what we already have, and it is 104BCD so only goes down to 30t right? I looked at these and passed 'em up for that reason.



Feldybikes said:


> 127mm cranks, a good length for 20" bikes, are easy to find on the Spawn site.
> 
> Alloy Cranks ? 127MM - Born to Ride | The World's Best Kids Bikes!
> 
> $60CAN ended up about $60USD including shipping with the currently US-favorable conversion rate.


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## Feldybikes (Feb 17, 2004)

Yeah. Guess I was focused on only your last paragraph where you were talking about a 20" bike and didn't see the connection to the rest of the post.I think a 30T ring is pretty damn small on a 20" wheel, but YMMV. A 30T on a 20" wheel results in a smaller gear than a 26T on a 24" wheel.


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## jwilds1 (Dec 21, 2013)

I'm really liking the idea of the Spectra eBay cranks (152mm triple; I would swap the big ring for a bash guard), but does anyone have any idea if there's a square taper BB that would fit into BB92? The frame I'm looking at is a BB92 - the next best thing I can find is a set of 165mm FSA cranks.


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## jestep (Jul 23, 2004)

Here's the spectra with the light aluminum bash guard and a 32T SNW chaining on it. Pretty respectable weight considering the cost and that most kids cranks come in somewhere around 2 - 4 lbs.

Even running 2x, something like 24T/ 36T / Bash, this would probably come out well under 700g.










Bash guard is very well made but pretty light aluminum and was only $12 so we'll see how long it lasts. Got it from BBG - MOUNTAIN | bbgbashguard


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## Mark194 (Mar 3, 2012)

Thanks for all the info everyone, I pulled the trigger on the Spectra's today. Hope they show up before Christmas


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## Miker J (Nov 4, 2003)

Need kids cranks? Easy...

Trailcraft Cycles

Call Trail Craft and speak with Ginger. Super to deal with and carry great kids bikes and components, including cranks.


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## Dreamerof1 (Jul 22, 2004)

ETChipotle said:


> I didn't know what size BB to get, and with the 113mm Shimano square taper it looks like I could use a spacer to improve the chain line. No hurry though, she doesn't shift out of low gear.


I'm getting ready to pick up a bottom bracket to use with my son's spectra's. Are you saying that a longer spindle would have improved your chainline(i.e. the chainrings are too far inboard)? How far off does it look?

Thanks


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## catch22 (Apr 30, 2004)

I don't think the GT Speed AL cranks have been posted in this thread yet. I just got some for my daughters Ripcord build and I'm really happy with them. I set out looking for a relatively affordable 2 piece, external BB, 104bcd crank with short arm length options. Seems like everything is either square taper (heavy) or 5 bolt (not small enough rings) so when I stumbled on these and given that the price was decent and they ticked all the boxes I ordered them hoping that the weight was okay. $150 and there are web coupons out there for this store to knock them down 15%. There were a couple other online shops that list them but they either didn't have sizes listed or the sites weren't quite as legit looking. J&R lists 135-165 in 5mm increments, I went with the 135s.

GT Speed AL Cranks at J&R Bicycles

Box included the crankset and the anodized blue external BB (looks like it's a Shimano Deore by the markings/seals) and ano blue chainring bolts. Cranks/chainring bolts are 558 grams and the external BB is 105 grams. Add a 30t N/W ring and it should be right at 693 grams for the setup. Dropped 409 grams from the stock square taper setup.


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## PMK (Oct 12, 2004)

Good option if we need to go smaller front than a 34 with a 34 rear on the 20" bike. Time will tell.

PK


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## Mark194 (Mar 3, 2012)

Dreamerof1 said:


> I'm getting ready to pick up a bottom bracket to use with my son's spectra's. Are you saying that a longer spindle would have improved your chainline(i.e. the chainrings are too far inboard)? How far off does it look?
> 
> Thanks


I went with a 106mm on a Giant 24. Puts the chain right in the middle of the rear cassette.


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## PMK (Oct 12, 2004)

BTW, for our 2016 20" Hotrock Girls build, I went with 140mm Origin 8 cranks, the BB length specified by Origin 8 and an Origin 8 chainring. Cost was reasonable. These are square tapers, and the BB is pretty light. Sealed bearings and spins silly good. Doubting my granddaughter will flex the BB spindle at 40 pounds.


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## backinmysaddle (Jul 27, 2011)

Thanks, these are really nice and I particularly like the BB upgrade. A couple of questions:
(1) how is the 30t working out on steeps, what is the large rear cog size?
(2) what is the threading on the BB? I have no idea if the threading on my son's bike (currently has threaded square taper BB) would accept this BB.
(3) what is the width of the BB shell, the bike my son has is really narrow (which is good for his small body) but I am not sure these would work as a result.



catch22 said:


> I don't think the GT Speed AL cranks have been posted in this thread yet. I just got some for my daughters Ripcord build and I'm really happy with them. I set out looking for a relatively affordable 2 piece, external BB, 104bcd crank with short arm length options. Seems like everything is either square taper (heavy) or 5 bolt (not small enough rings) so when I stumbled on these and given that the price was decent and they ticked all the boxes I ordered them hoping that the weight was okay. $150 and there are web coupons out there for this store to knock them down 15%. There were a couple other online shops that list them but they either didn't have sizes listed or the sites weren't quite as legit looking. J&R lists 135-165 in 5mm increments, I went with the 135s.
> 
> GT Speed AL Cranks at J&R Bicycles
> 
> Box included the crankset and the anodized blue external BB (looks like it's a Shimano Deore by the markings/seals) and ano blue chainring bolts. Cranks/chainring bolts are 558 grams and the external BB is 105 grams. Add a 30t N/W ring and it should be right at 693 grams for the setup. Dropped 409 grams from the stock square taper setup.


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## catch22 (Apr 30, 2004)

backinmysaddle said:


> Thanks, these are really nice and I particularly like the BB upgrade. A couple of questions:
> (1) how is the 30t working out on steeps, what is the large rear cog size?
> (2) what is the threading on the BB? I have no idea if the threading on my son's bike (currently has threaded square taper BB) would accept this BB.
> (3) what is the width of the BB shell, the bike my son has is really narrow (which is good for his small body) but I am not sure these would work as a result.


Well, the plan is to run the 30t up front paired with a 11-36 rear to start but I may throw a spare 42t cog I've got on there to see how it shifts. With the shorter stays of the 24" I'm thinking the chainline of the 42t might be a bit too much. This is going on a bike for her 7th birthday in January so I won't be able to review much for a bit. I'm probably a good 2-3 weeks from having the wheelset built that is going on the frame so I won't be testing much in terms of gearing, chainline, etc. til then. These are standard english/BSA threaded cups so they should swap right in for the square tapered setup you are working with. I didn't put a caliper on the BB but I'd be shocked if it wasn't setup for a standard 73mm mountain BB shell (and would be pretty surprised if that wasn't what you had). Hope that helps, I'll try to get some updates once I've got it all together (hoping for mid-Dec.).


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## TigWorld (Feb 8, 2010)

catch22 said:


> ... I'm thinking the chainline of the 42t might be a bit too much...


On my daughter's XS 26er with a 40t rear cog, the chainline was touch and go with a 30t front chainring aligned with the middle of the cluster. It gets worse if you have a longer caged derailleur as in the big ring the chain is tightest as the lower jockey wheel can extend a long way forward (effectively shortening the space the chain has to do its "diagonal" thing). You can see what I mean in this pic:



The derailleur at the time was a short cage XTR, but I subsequently replaced that with a 9 speed clutched XTR mash-up that I put together.



It has been an excellent setup but I did have to space the 30t cog slightly inboard (3mm) to get it to work properly (and that's with a relatively short RADr cage).


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## othello (Apr 10, 2012)

Has anyone tried a set of Redline microline 2-piece cranks? They seem to come in a range of sizes, and have an external bottom bracket. 

I'm looking at a pair for my daughters new road bike (she has the Utah trikes 152mm on her MTB), and want 155mm cranks with a 110BCD. But I don't want a square taper bb, and there is hardly any choice for external bearings. I spotted the Redlines and they look good. It doesn't say if you can run a double chainring set-up though.


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## backinmysaddle (Jul 27, 2011)

This was great to learn, turns out the threads are the same size so I put in a spare external style Deore BB and it fits well. The shell on my BB is actually slightly narrower than standard size (one of the selling points of the IslaBike is the narrower space between pedals for small kids). I did put some spacers in and got an extra pair of HollowTechII cranks to work just fine, they are way too long for a kid of course, but found they are not suitable for shortening (at least that is what the crank shortener guys site says).

So now I love the idea of the lighter external BB, and can't bear to put a square taper back on, just really would like to find something in 150mm range that will allow 28t front ring. I have tried 28t Front and 38t Rear and it is perfect, so really want to find a 28t compatible 2 pc crankset.

The BMX 2 pc cranksets are either 110BCD (min 32t) or 104BCD (at least can squeeze a 30t on there), anyone know of a 2 piece (non square taper) 2x crankset that comes in sub 160mm crank arm length? At least with a 2x I can put a sub-30t ring on as the smaller ring.



catch22 said:


> Well, the plan is to run the 30t up front paired with a 11-36 rear to start but I may throw a spare 42t cog I've got on there to see how it shifts. With the shorter stays of the 24" I'm thinking the chainline of the 42t might be a bit too much. This is going on a bike for her 7th birthday in January so I won't be able to review much for a bit. I'm probably a good 2-3 weeks from having the wheelset built that is going on the frame so I won't be testing much in terms of gearing, chainline, etc. til then. These are standard english/BSA threaded cups so they should swap right in for the square tapered setup you are working with. I didn't put a caliper on the BB but I'd be shocked if it wasn't setup for a standard 73mm mountain BB shell (and would be pretty surprised if that wasn't what you had). Hope that helps, I'll try to get some updates once I've got it all together (hoping for mid-Dec.).


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## Rue (Jan 4, 2015)

Great minds think alike?

Pic didn't upload...I have same setup



jestep said:


> Here's the spectra with the light aluminum bash guard and a 32T SNW chaining on it. Pretty respectable weight considering the cost and that most kids cranks come in somewhere around 2 - 4 lbs.
> 
> Even running 2x, something like 24T/ 36T / Bash, this would probably come out well under 700g.
> 
> Bash guard is very well made but pretty light aluminum and was only $12 so we'll see how long it lasts. Got it from BBG - MOUNTAIN | bbgbashguard


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## jwilds1 (Dec 21, 2013)

I'm in a quandary with crank length, and looking for some guidance.

In the coming months, I'm going to be building up an XS 26er for my 11-year old son. I measured him up last week, and came up with a 25.5" inseam (true inseam). Gearing will likely be 1x9 or 1x10, with a 26- or 28- chain ring and a cassette that tops out at 36 teeth.

His current 24" bike has a 14-28 cassette and the smaller two rings are 32/22.

Using Sheldon's gain ratio:
Current 24" bike 152mm cranks, 22T crank gear, 28T rear = gain ratio of 1.6
New 26" bike *160mm cranks*, 28T crank gear, 36T rear = gain ratio of 1.5
New 26" bike *170mm cranks*, 28T crank gear, 36T rear = gain ratio of 1.4

My goal is obviously to get something that's comfortable, but also get him some more gear to tackle hills with. Also, hitting the 170mm bogey opens up a lot of choices, 165mm less-so, and 160 and below I'm pretty limited.

What are your thoughts?


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## ladljon (Nov 30, 2011)

Turn3Racing....I have a 29" inseam, running 125mm and 135mm. Wished I had short crank thirty yrs ago....


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## ETChipotle (Sep 20, 2014)

I'm not seeing those Spectra cranks on Ebay anymore, but now Trailcraft is here


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## Feldybikes (Feb 17, 2004)

Not as useful for really little kids, but new SRAM NX cranks go down as low as 155mm:

SRAM releases a full 1x11 group for $310. This is good news for all.


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## TigWorld (Feb 8, 2010)

That is good news. Pity they are not direct mount like other SRAM cranks, but I suppose we can't have everything.


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## carbon.bike (Mar 17, 2016)

I went through all of this for my older kids.**For the younger kids I just made the solution.**I know this is a bit spammy but I desperately want this to work so that 1. my wife doesn't kill me over what I have sunk into it.**2.**I want to make carbon kids bikes, for about what the big guys sell these 26lb turds.***Next thing in the shop is thru axle disc forks in 20/24/26 then frames.**Forge the joints, bond tubes.**I have rim aluminum extrusion done for disc 20/24/26 in china tubeless compatible but I am still searching for 20" tires.**And a 38t cassette around 200g.**Those are on the Facebook.
So save a life and lighten the kids/wife's or even your bike up by supporting this indiegogo https://igg.me/at/forgedcarbon 
Any shares/likes/tweets/shouts are greatly appreciated.
cheers


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## svj (Feb 1, 2014)

I just bought some 135mm cranks from these guys- https://www.facebook.com/turn3racing and with a 28tooth 94bcd wolftooth chainring they weigh ~400grams.


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## jestep (Jul 23, 2004)

catch22 said:


> Well, the plan is to run the 30t up front paired with a 11-36 rear to start but I may throw a spare 42t cog I've got on there to see how it shifts. With the shorter stays of the 24" I'm thinking the chainline of the 42t might be a bit too much. This is going on a bike for her 7th birthday in January so I won't be able to review much for a bit. I'm probably a good 2-3 weeks from having the wheelset built that is going on the frame so I won't be testing much in terms of gearing, chainline, etc. til then. These are standard english/BSA threaded cups so they should swap right in for the square tapered setup you are working with. I didn't put a caliper on the BB but I'd be shocked if it wasn't setup for a standard 73mm mountain BB shell (and would be pretty surprised if that wasn't what you had). Hope that helps, I'll try to get some updates once I've got it all together (hoping for mid-Dec.).


Were you able to confirm these work on a 73mm BB width? I've looked everywhere and can't determine if they will work on 73, or if a bmx BB width is typically 68. DOing a build and it doesn't look like the SRAM NX cranks are out yet, so was looking at these as another option.


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## Surfpoodi (Sep 14, 2011)

i have a used 140 mm square taper AC MiniLE crankset if anyone is interested. Can include 34t ring. PM me if interested.


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## jestep (Jul 23, 2004)

Just confirmed the GT Speed Al cranks do not fit a 73mm frame.

The crank shortening option on bike smith design is down as well, not sure if this is temporary, but if so leaves the SRAM NX basically the only option for short external cup cranks on a 73mm frame.


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## gtrguy2 (May 17, 2015)

jestep said:


> Just confirmed the GT Speed Al cranks do not fit a 73mm frame.


Spindle length only enough for 68mm BB shells?


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## jestep (Jul 23, 2004)

gtrguy2 said:


> Spindle length only enough for 68mm BB shells?


I guess that's why, they were a bit vague in their response. It's possible that it would work but the included BB is made for 68mm so I guess it might cause issues if the plastic tube can't properly sit in the BB cups. 5mm does sound like enough of a gap that the arm could end up getting smashed against the outside of of the cup when tightening.

Anyway, I don't really feel like taking a $120 risk on it, so if anyone has successfully used one, with or without the included BB, I'd definitely still like to know.


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## BullSCit (Mar 26, 2004)

After looking at all the possibilities, I ended up getting the Bombshell Spinnergy Mini cranks. For about $275 I got lightweight cranks in the size I want (140), with a 30T narrow wide ring along with a ceramic BB. Hopefully it all comes together.


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## murrdogg11 (Apr 4, 2010)

nice looking set of kids cranks, 155mm and direct mount. 
Brood Bike Co. Styx Direct Mount Crank - 155mm - Parts - Gear - Born to Ride | The World's Best Kids Bikes!


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## jestep (Jul 23, 2004)

murrdogg11 said:


> nice looking set of kids cranks, 155mm and direct mount.
> Brood Bike Co. Styx Direct Mount Crank - 155mm - Parts - Gear - Born to Ride | The World's Best Kids Bikes!


Those look killer with the direct mount ring. They don't post the weight but probably decent.


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## BullSCit (Mar 26, 2004)

murrdogg11 said:


> nice looking set of kids cranks, 155mm and direct mount.
> Brood Bike Co. Styx Direct Mount Crank - 155mm - Parts - Gear - Born to Ride | The World's Best Kids Bikes!


Dang, wish I had seen these before. They must have just added them, as I'm sure I checked Spawn to see if they had any alternatives. Will definitely keep these in mind for the next bike though.


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## murrdogg11 (Apr 4, 2010)

BullSCit said:


> Dang, wish I had seen these before. They must have just added them, as I'm sure I checked Spawn to see if they had any alternatives. Will definitely keep these in mind for the next bike though.


they seem to only be on their canadian site.


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## dav3epohl (Feb 17, 2010)

I had this issue a couple years ago with my son's 20" bike. Ended up getting a set of Sinz cranks (110 BCD) and pairing them with an IRD tripleizer chainring I already had so I could add a smaller inner ring. It made for a nice 2 ring setup and the chainline was fine with the stock bb.


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## gtrguy2 (May 17, 2015)

jestep said:


> Anyway, I don't really feel like taking a $120 risk on it, so if anyone has successfully used one, with or without the included BB, I'd definitely still like to know.


Decided to give a set of these a try for my son's bike. I should have them in a week or so and will let you know what the deal is as far as the compatibility with a standard threaded BB.


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## gtrguy2 (May 17, 2015)

jestep said:


> Anyway, I don't really feel like taking a $120 risk on it, so if anyone has successfully used one, with or without the included BB, I'd definitely still like to know.


Just to follow up- got the GT cranks and fitted them to my son's Stinky. No problems whatsoever. I didn't bother to change the bottom bracket and just left the Shimano in there and everything went together fine.


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## azorr (Jul 9, 2012)

Thanks to this thread I just ordered a set of the GT cranks in 150mm for the bike I am building my son. They had a $5 coupon code for signing up for their email list, with that they came out to $100 shipped.


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## jochribs (Nov 12, 2009)

jestep said:


> I guess that's why, they were a bit vague in their response. It's possible that it would work but the included BB is made for 68mm so I guess it might cause issues if the plastic tube can't properly sit in the BB cups. 5mm does sound like enough of a gap that the arm could end up getting smashed against the outside of of the cup when tightening.
> 
> Anyway, I don't really feel like taking a $120 risk on it, so if anyone has successfully used one, with or without the included BB, I'd definitely still like to know.





gtrguy2 said:


> Just to follow up- got the GT cranks and fitted them to my son's Stinky. No problems whatsoever. I didn't bother to change the bottom bracket and just left the Shimano in there and everything went together fine.


What's the BB shell width on the Stinky though? I think what Jestep is concerned with is if the cranks spindle can accommodate the extra 5mm of width with a 73mm shell and still have enough clamping area for the left arm. Not to mention that the bearing surfaces on the spindle will be off set and not fully (if at all) supporting the bearing on the non drive side...


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## gtrguy2 (May 17, 2015)

Valid points. The Stinky is a 68mm shell but since I'm using a Hollowtech II BB, it's spaced to 73mm. I was happy with the fit as far as the amount of spindle clamping area for the non-drive side arm and where the spindle was sitting in the non-drive bearing. In my case I have the option of dropping the spacers the decrease the overall width but didn't feel it was necessary. YMMV.


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## jochribs (Nov 12, 2009)

I think you can take the spacers out. If you have spacers on both sides to even out the cups, then the bearings are only riding on 1/2 the spindles bearing surfaces on each side. The sealed spacer that runs between the cups is designed to work with both 68 and 73 by way of an o-ring fit on the non-drive side I'm pretty sure.

Edit...there's a good chance that I am wrong on that with the Shimano BB. I just pulled out my XTR BB that has sat in the box since I got my cranks and it is dedicated at 73 with no way to adjust the width due to the seal/spacer.


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## gtrguy2 (May 17, 2015)

The Shimano BB I'm using is good for 68mm or 73mm- I didn't realize they even made dedicated 73mm versions, I've never seen one. Are you sure about that?

I just couldn't be bothered to pull the spacers. If the spindle length had been much shorter I would have.

A couple of other notes about the crankset- JR list it as having an aluminum spindle but it's not. Also, the crank arm attachment interface is a bit odd- the spindle has large-ish splines like an ISIS BB but uses a bearing preload adjuster and pinch bolts like a Hollowtech II.


Also, it doesn't matter how many spacers you use, the drive side of the spindle bearing surface will still sit 100% in the right place. That's not true of the non-drive side though, the amount of spacers will affect that.


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## jochribs (Nov 12, 2009)

Yeah I'm sure, just measured it. Choice is 73, and 73 . The spacer has hard steps on each end and doesn't allow adjustment.

Ditto on the spindle material. Pissed me off a bit, but hey, they were only 95 bucks. Let me guess, you got them from J&R? I just got the last pair of 135's. Weren't even on the site, but I called to ask about the others, thinking I'd just cut them down, and he said they were out in the race trailer! Woohoo! Last ones! LOL! 

Those cranks really disappeared quickly. I put this stuff on the back burner for snowboard season, and when I checked again, stuff was already done gone..

Edit...duh, you said that you got them from J&R...I'm doing A LOT of edits today. Reading comprehension and all that.


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## gtrguy2 (May 17, 2015)

The GT Speed cranks come and go from the J&R site, I've been watching them for a long time.

Regarding the BB- for a 68mm shell, the extra space is normally taken up by the spacers. The overall width once the cups are installed in a 68mm or 73mm shell is the same.


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## jochribs (Nov 12, 2009)

Not sure they'll be coming back this time, although that would be good for everyone else if they did. Talking with GT, they aren't making them anymore...

It's SM-BB90A Came with my M980 Trail cranks.


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## 2melow (Jan 5, 2004)

jochribs said:


> Ditto on the spindle material. Pissed me off a bit, but hey, they were only 95 bucks.
> 
> Those cranks really disappeared quickly.


Trailcraft Cycles has aluminum spindle direct mount cranks in 140mm and 152mm lengths now with 26, 28, and 30t chainrings in stock. Same cranks as what are on the PRO builds.

Another option if the GT cranks are really discontinued.

Trailcraft Cycles


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## Steve-XtC (Feb 7, 2016)

Does anyone know if the direct mount is inter-changable with SRAM direct mount? 
(looks like it should be so if you wanted larger than 30T you could use any SRAM direct mount?)


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## jochribs (Nov 12, 2009)

Is there a difference between direct mounts, or is it a standard interface between anything that is referred to as direct mount? 

The Trailcraft direct mounts look like a good option. Are the arms hollow?


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## gtrguy2 (May 17, 2015)

There are a couple of different direct mount styles- Raceface DM and SRAM DM are not the same thing and are not interchangeable. If I recall correctly, the Trailcraft cranks use the SRAM style.


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## jestep (Jul 23, 2004)

Just for reference: https://www.wolftoothcomponents.com/collections/mountain

They make rings for most DM and spidered setups. There's quite a few DM options, definitely not anything close to universal.


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## backinmysaddle (Jul 27, 2011)

2melow said:


> Trailcraft Cycles has aluminum spindle direct mount cranks in 140mm and 152mm lengths now with 26, 28, and 30t chainrings in stock. Same cranks as what are on the PRO builds.
> 
> Another option if the GT cranks are really discontinued.
> 
> Trailcraft Cycles


These are sweet, finally somebody built the right crank for kids!


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## murrdogg11 (Apr 4, 2010)

this looks like a good, cheap option. why would they not be compatible with a 113mm bb? would they work with any other size?
https://www.universalcycles.com/shopping/product_details.php?id=76620
104bcd so should be an easy 1x set-up.

opinions?


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## jochribs (Nov 12, 2009)

I'd say it would most likely be because running it as a 3 ring, with a 113 bb, you might run into interference issues with the rings on the frame in some applications, and then again, sometimes not. Or it could be that the taper section of the crank might bottom out on the cup before it is on tight enough, due to the spindle being shorter. 

Best way to find out would be to give Suntour a call or an email and ask them. For what you want to do with it, it may be fine, but you never know.


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## Miker J (Nov 4, 2003)

2melow said:


> Trailcraft Cycles has aluminum spindle direct mount cranks in 140mm and 152mm lengths now with 26, 28, and 30t chainrings in stock. Same cranks as what are on the PRO builds.
> 
> Another option if the GT cranks are really discontinued.
> 
> Trailcraft Cycles


Trailcraft has good stuff for kids and they are good to work with.

Are those rings narrow/wide?


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## jochribs (Nov 12, 2009)

Yeah, trailcraft has their own branded NW rings.


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## thesmokingman (Jan 17, 2009)

Imo, if you're going for the 152mm crank, I'd rather go with the Sram NX in 155mm for the wider selection of rings. I'd also rather replace a ring than a spider or have to throw in more money for a wolf spider and ring combo.


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## murrdogg11 (Apr 4, 2010)

thesmokingman said:


> Imo, if you're going for the 152mm crank, I'd rather go with the Sram NX in 155mm for the wider selection of rings. I'd also rather replace a ring than a spider or have to throw in more money for a wolf spider and ring combo.


pretty sure both of these cranksets have a 104bcd...how would the sram have a better selection of rings?


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## thesmokingman (Jan 17, 2009)

murrdogg11 said:


> pretty sure both of these cranksets have a 104bcd...how would the sram have a better selection of rings?


The hollow trailcraft cranks are direct mount and use a spider. The trailcraft cranks that use rings are not hollowtech. Also the NX is 94mm BCD and ring choices run the gamut.


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## murrdogg11 (Apr 4, 2010)

thesmokingman said:


> The hollow trailcraft cranks are direct mount and use a spider. The trailcraft cranks that use rings are not hollowtech. Also the NX is 94mm BCD and ring choices run the gamut.


oh sorry i thought you were talking about the sun tour cranks i posted above...ive been looking at them and others and having a hard time getting past the $30 price point..... cheap bb and readily available nw rings with 104bcd. i guess the only real draw back could be weight, but how much could it be?


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## thesmokingman (Jan 17, 2009)

murrdogg11 said:


> oh sorry i thought you were talking about the sun tour cranks i posted above...ive been looking at them and others and having a hard time getting past the $30 price point..... cheap bb and readily available nw rings with 104bcd. i guess the only real draw back could be weight, but how much could it be?


Those suntour cranks iirc are in the 920+ grams range w/o a BB. Add in a 300 gram BB and well it's real heavy!

Another thing to think about is that at 152mm and up we're getting close to adult sizing, meaning the kids are about to hit their teens and sprout. That's why I'd go for the NX crank for its flexibility, and besides that I 'd want to stick to an external BB, so moving it to a bigger frame as they grow to a 26in. It's easier to do this and more worthwhile to keep and reuse with the NX or Trailcraft. Btw, those trailcraft prices are steep, replacement spiders are 45 bucks!


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## murrdogg11 (Apr 4, 2010)

thesmokingman said:


> Those suntour cranks iirc are in the 920+ grams range w/o a BB. Add in a 300 gram BB and well it's real heavy!
> 
> Another thing to think about is that at 152mm and up we're getting close to adult sizing, meaning the kids are about to hit their teens and sprout. That's why I'd go for the NX crank for its flexibility, and besides that I 'd want to stick to an external BB, so moving it to a bigger frame as they grow to a 26in. It's easier to do this and more worthwhile to keep and reuse with the NX or Trailcraft. Btw, those trailcraft prices are steep, replacement spiders are 45 bucks!


ya thats a good point.....a good chunk of weight. i think you would lose a couple hundred grams taking off those steel chainrings though.


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## jochribs (Nov 12, 2009)

Smokingman, the direct mounts, get a chainring mounted 'directly'...there is no spider. 

And 45 bucks for a direct mounting narrow wide chainring seems like a good deal to me, considering that a much lesser machined 'ring' for 104 bolt pattern will set you back in the range of 50-70 bucks. (Race Face, Wolf, One Up etc.)

Not to mention, for 159 you're getting cranks, BB, and direct mount chainring. Shyte, if my son needed 140's or longer I'd have just gotten them. It's a no brainer. Solid, future proof, good looking crank...(that's what she said!)

Sorry, I've been watching Office re-runs...


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## thesmokingman (Jan 17, 2009)

Doh, I wrote spider but meant sprocket. Or is that too bmx? lol And yea, 160 is decent for crankset with bb. I prefer a spider setup for flexibility, use of shims, slap on a bashguard, quick ring change, etc etc. As for rings on the NX, why go aftermarket when you can buy Sram X-sync for 20 bucks? But as I wrote before it's preference.


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## Steve-XtC (Feb 7, 2016)

murrdogg11 said:


> ya thats a good point.....a good chunk of weight. i think you would lose a couple hundred grams taking off those steel chainrings though.


You won't lose the 300g bottom bracket though .. except you might have to anyway as the 3x will likely not have the correct chainline if fitted with a decent quality crankset....

Then you need to buy the new ring(s) anyway.... and you are still stuck with a boat anchor BB/cranks and they are 152mm ANYWAY.....

If your going to do it I'd do it properly.... you can buy brand new SRAM S600's in square taper for not much more.then cut to the right length.. and change the BB while at it to the UN55....

I paid GBP£15 ($20?) for some used Alivio's which cut down to 140mm... (I'd say as short as they can be cut) the SRAM's can go even shorter... and both take a standard 104 BCD

When he needs 152 ... I'll get some NX 155's... on his race bike but if it wasn't a race bike I'd just go for another set of cut down cranks at 150mm once 140 is really too small.

Meanwhile I'm considering the Trailcraft but would need to know they are SRAM direct mount .... as annoyingly I'd need to have a few front chainrings as well... and he pushes 34 on the "kids XC" which is really more like cyclo-cross and has a lot of paved and non technical...

I can honestly say I'd never use the Suntours that were supplied.... they are terrible in almost every way.... from chainline to weight to Q-factor to the actual fit onto a BB....


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## murrdogg11 (Apr 4, 2010)

Steve-XtC said:


> You won't lose the 300g bottom bracket though .. except you might have to anyway as the 3x will likely not have the correct chainline if fitted with a decent quality crankset....
> 
> Then you need to buy the new ring(s) anyway.... and you are still stuck with a boat anchor BB/cranks and they are 152mm ANYWAY.....
> 
> ...


roger all of that...thanks.


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## jochribs (Nov 12, 2009)

If anyone is interested, I have the 152 arms from the Orbea MX24. They weigh 563 stripped down.


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## Steve-XtC (Feb 7, 2016)

murrdogg11 said:


> roger all of that...thanks.


Yep sorry a bit long winded way to put it...

The price difference on the SRAM S600's is minor .... (Amazon UK its £10 difference) 
The difference in quality feels huge though...

Even Shimano UN55 BB's are cheap.... (well even their XT/XTR level HT II BB's are cheap compared to most bike stuff)

so between them you get a pretty good improvement for very little $$$ and since you are upgrading anyway it seems like one of those things to try and do properly..

Once you invest in the pedal taps (I found mid range work perfectly as its soft alloy not steel) then you can make a new set up as and when needed for very little outlay... (this is how i got the Alivio's as they were just on ebay for not much more than postage costs)

Probably also fair to warn you though... this can get quite addictive.... 
I started off donating spares from my bike to the kids bike.... a year or a bit more later it's reversed


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## murrdogg11 (Apr 4, 2010)

I bit the bullet and ordered the spawn 155mm cranks with direct mount... Should be here next week. I'll post some weights.


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## murrdogg11 (Apr 4, 2010)

https://spawncycles.com/brood-eldorado-syx-140

If anyone is curious the 155mm crank arms/spindle weighed in at 600g
Bb is 110g without the spacers


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## martinizer (May 2, 2011)

jochribs said:


> If anyone is interested, I have the 152 arms from the Orbea MX24. They weigh 563 stripped down.


So that's cranks minus bash guard and chainring, right? Any idea how much that square taper bottom bracket weighs?


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## Steve-XtC (Feb 7, 2016)

martinizer said:


> So that's cranks minus bash guard and chainring, right? Any idea how much that square taper bottom bracket weighs?


Not exactly as we didn't write it down but it's lighter than a UN55.

It was a bit of rush as a friend came over with his kid and a MX24 he'd picked up (cheapest possible no discs etc.) and we did a rebuild from our spares bins.

I had a spare set of S600 cranks I'd shortened to 140 and UN55 but when we pulled the B.B. and weighed it was less and good condition so we put it back in.


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## thesmokingman (Jan 17, 2009)

ST BB's are usually around 300 grams and up, not exactly light. The UN26 Shimano for instance is 355 grams. With a 560gram crank, that's 1k grams roughly, then there's the bolts too.


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## xprmntl (Oct 4, 2006)

*FS Orbea MX 24 Trail Cranks*

I have an unused set of the Orbea 152 mm cranks with 32T chainring and square taper bottom bracket. $50, shipped. PM me for pics, questions and/or purchase


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## Steve-XtC (Feb 7, 2016)

thesmokingman said:


> ST BB's are usually around 300 grams and up, not exactly light. The UN26 Shimano for instance is 355 grams. With a 560gram crank, that's 1k grams roughly, then there's the bolts too.


The UN55's are quite a bit lighter and still only a few $$ 
The overall weight difference between Shimano external BB with Zee cranks cut to 140 vs the SRAM S600's at the same length and UN55 was 12g (from memory).

I just checked an old photo and the SRAM's + 118mm UN55 + 30T chainring and all bolts weigh 876g.

Trailcraft 140mm with 30T are quoted as 558g. I'm not sure if this includes BB but that's 113g (and I'm guessing not or they wouldn't list separately)... so if its without then that's 671g vs 876g and $160 vs 200g weight saving. (Which is quite a bit less than say 2 inner tubes or less than the difference in saddle weight between the stock one came with my kids bike vs the $15 one I replaced it with)

All that said the price of the Trailcraft direct mount is good (compare with any half decent adult one) *but its not good for us* (because I'd need to buy extra direct mount chainrings when I have a stock of 104BCD and as a minimum he'd need a 34T as well. Or I'd need to go to more expense of fitting a SRAM XD driver and a 10T cassette.)

We ability of fitting a smaller chainring than a 30T has no utility for us but if for some reason you need a smaller chainring then that would be different.

At the end IMHO the benefits of having the correct sized cranks are huge compared to 200g of weight... 
However the benefit of almost anything half decent over the Suntour kids cranks is also huge... the are just really poorly made. The difference in quality over the cheap SRAM's is like night and day... not just the chainrings but the way they fit (or don't really fit*) onto the BB...

*The suntour cranks we had didn't fit onto the BB as such.. they sorta got rammed on by the bolts until the poor tolerance square taper got deformed enough to fit on... it's probably a mis-representation to call them square taper even... (as the manufacturing tolerance hardly approximated a square... granted it had 4 sides but all slightly different lengths)


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## xprmntl (Oct 4, 2006)

The SR Suntour XCT Jr. Crankset that Steve-XTC references uses a JIS square taper standard, so was likely mated with an ISO square taper bottom bracket, hence the fit issue. They can be forced to fit but mating is poor and it generally ends up loosening.


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## ladljon (Nov 30, 2011)

Give [email protected] a shout....they will take care of all your problems. Update; 5' with 27" inseam...been riding 135mm on mtb and cx, 125mm on road bike for a few yrs. Wished I had known this twenty yrs ago. Find Turn3 racing on FB.


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## Acrophylos (Jun 10, 2018)

SRAM Rival with removable spider is easy to shorten, and mount whatever size direct mount chainring you want!


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## MXIV424 (May 30, 2018)

Oh this is great. I found this looking for cranks to go on a hardtail 13" 27.5 frame I'll be building up for my daughter.

So the turn 3 cranks look super light but use a square taper BB thats fairly heavy. They list 125mm cranks at 373g, so guessing 155mm at 420g ish? Then a BB at around 180g for $90 and ring and bolts at 60g for 50 bucks. So total weight at 660g for $296

Then trailcraft DM is at 582g for 30t 152mm and 113 for BB, so 695g for $160

Sram nx 155mm is claimed at 680g with 32t. Add 118g for bb for $30 and its 798g for about $135


Thinking I'm going Trailcraft for now. I'm hoping to see other options become available as well!


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## xprmntl (Oct 4, 2006)

I went with the NX because it will take a 28T. That coupled with an 11-42T (Sunrace) cassette, makes for a considerably better low than a 30T and works with a 10 Spd med cage rear derailleur


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## 2melow (Jan 5, 2004)

xprmntl said:


> I went with the NX because it will take a 28T. That coupled with an 11-42T (Sunrace) cassette, makes for a considerably better low than a 30T and works with a 10 Spd med cage rear derailleur


Trailcraft Direct Mount's can go down to a 26 tooth, and use an aluminum spindle to save weight over steel spindle.

For reference, just replaced a NX crankset off a Transition Ripcord (30 tooth, 155mm length) and replaced it with a Trailcraft 152mm and 26 tooth for a better mountian climbing gear.

SRAM NX 155mm with 30t and bb = 810g

Trailcraft 152mm with 26t and BB = 665g

145g savings over stock NX setup, so not a ton but taking 145g off the bike in 4-5 places is well over a pound.


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## xprmntl (Oct 4, 2006)

That Trailcraft direct mount option is cool. It wasn't available this past winter while I was swapping out a few parts on my daughter's 24" Orbea MX Trail. 

It's all trade-offs, though, right? At the time, I wanted a reasonable way to get that bike to ~16 gear inches. That was accomplished with the 28T x 42T combo with 24" wheels and 155 mm crank arms

More numbers for those considering similar (using numbers off google searches)...

Trailcraft 152mm with 26t: 570g + Trailcraft BB 113 g (total 683g) $160

SRAM NX 155 mm with 32t - 680 g $92 
GXP Team bottom bracket: ~115 g (varies) $25
Aftermarket narrow-wide 28T $30 (sell SRAM 32T for $35) -$5, -10g
Total: 785g; $117

In choosing a chainring size, a 26T seems like a good idea for a kid, but that 2T difference from 28T doesn't keep from having to use a newer high range cassette to get a good low gear. I consider a "good low gear" as one equivalent in gear inches to a 22T x 36T on a 26" bike with 175mm which is ~15.9 gear inches (according to the Sheldon Brown calculator). 
For a 24" bike and 152/155 cranks:
26T x 36T = 17.3 gear in
26T x 40T = 15.6

28T x 42T = 16.085g

Shimano XT 11x36T 9spd $50, ~300g
Shimano XT 11x36T 10spd $50, ~340g
Sunrace MX3 11x40T 10spd $45, ~ 380g
Sunrace MX3 11x42T 10spd $45, ~390g (~430g for Shimano M8000)


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## Steve-XtC (Feb 7, 2016)

> In choosing a chainring size, a 26T seems like a good idea for a kid, but that 2T difference from 28T doesn't keep from having to use a newer high range cassette to get a good low gear. I consider a "good low gear" as one equivalent in gear inches to a 22T x 36T on a 26" bike


I consider a good low gear as one that i can ride up the steepest and longest hills I ride. 
If I had stuck with gear ratio's I'd never have gone 1x....

Having gone 1x I quickly found I didn't actually need most of the low gears I had been using... probably more surprisingly I found it was actually easier overall without them.

Whatever the gear ratio was on my 2x it got used and I got stuck in it. Stick it in 1st 200' into a 3000' climb for a steeper bit and getting out of it gets harder... every root and rock becomes a static challenge more than a rolling challenge because I don't have the momentum.

Looking back the whole 3x and 2x was with exceptions like carrying tents just part of the bigger and wider is better. 
We were given gears that made it harder and convinced ourselves to an extent they were needed based on once we used them. Even with my current set-up I've done a ride not realising I hadn't got my mech adjusted and didn't have 1st gear and not missed it.

With the kid I found this even more so... when he 1st had a 40T expander he was using it all the time... and once in it on a climb getting out of it was difficult. I took it off one day and didn't say anything and he did fine... he didn't even notice the missing gear he'd been using ..


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## jochribs (Nov 12, 2009)

Steve-XtC said:


> With the kid I found this even more so... when he 1st had a 40T expander he was using it all the time... and once in it on a climb getting out of it was difficult. I took it off one day and didn't say anything and he did fine... he didn't even notice the missing gear he'd been using ..


Totally agree with ya Steve. I went ahead and threw a Sunrace 11-42 10spd cassette on my sons hardtail. Grabbed an 11 spd XT rear derailleur to handle the larger cog. He isn't completely enthralled with the steps between the lower gears and on the hardest/techiest climbs he just isn't using the 42. He'd been running an 11-36 previously. 30t front.

I myself ride a 36t front to an 11-34 rear. I don't think I'm super human. I don't have any problems. Like father like son, I guess.


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## GSJ1973 (May 8, 2011)

Steve-XtC said:


> Having gone 1x I quickly found I didn't actually need most of the low gears I had been using... probably more surprisingly I found it was actually easier overall without them.


Yes! Dropping the 3x, front shifter, all the housing and complications was the best move we ever made by going 1x. Do it!


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## RMCDan (Feb 28, 2008)

jochribs said:


> I myself ride a 36t front to an 11-34 rear. I don't think I'm super human. I don't have any problems. Like father like son, I guess.


You're a harder man than I.

#humblebrag #saystheguywholivesinjersey

j/k


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## svinyard (Aug 14, 2017)

RMCDan said:


> You're a harder man than I.


Jochribs, 32in waist, 34in quads. Can only bike in early 90's MC Hammer pants.


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## jochribs (Nov 12, 2009)

Lol!! 

Make that 31 inch waist.

Don't be jealous. Just turn your cranks


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## jochribs (Nov 12, 2009)

Svinyard, just recently started riding. Is now the authority on all things bro bra. Son will lay the coals to him in maybe year. (That's his son. My son probably already can)


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## MidnightFattie (Jun 13, 2017)

I worry about crank length for my kid, too, especially after reading this forum. But then there are kids like this, riding bike that do not fit at all, long cranks, heavy 30+ pound bikes, improper leg extension...yet nonetheless developing ridiculous skills and connection to their bike.

It's amazing what kids can do when motivated, and nothing motivates them more than their peers.






I have to remind myself when I get on these shopping missions that if my kid isn't keeping up, there may be other things more important than crank length.


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## svinyard (Aug 14, 2017)

You sure those are crap bikes? I mean weight in a BMX/DJ hybrid bike isn't the same situation as with little kids trying to climb distance and throw a bike around at high speeds over chunk on single-track. It's a high stakes game for little groms, maybe THE most high stakes game you'll see a kid play. I love the rigid bikes there. Wish people would buy those instead of the crappy Riprock style stuff.


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## jochribs (Nov 12, 2009)

Not sure some kids 'walking the bike' is an argument for cranks that are too long. 

As Svinyard brings up, there's a massive difference between that and putting in repetitive cadence and pyshing out watts on a bike meant for covering distance, and tech riding. 

Plus bmx bikes generally have longer cranks as you are standing the majority of the time. That kids have fresh synovial flyid in their joints is not withstanding in just figuring they should push longer cranks than is mechanically sound for those said joints. A 150 crank for a 4'6" kid is like us pushing a 200+mm crank. 

Would you like to push 200mm cranks? If you do, let us know how that goes. I'm not thinking too well.


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## thesmokingman (Jan 17, 2009)

MidnightFattie said:


>


It's like an SE sponsored wheelie inspirational video!


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## jochribs (Nov 12, 2009)

thesmokingman said:


> It's like an SE sponsored wheelie inspirational video!


No kidding.


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## thesmokingman (Jan 17, 2009)

jochribs said:


> No kidding.


Yea hehe. Oh and apparently Speccy will not be out done!


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## david.p (Apr 11, 2011)

While doing a build for my 12yo I came across these Suntour Zeron cranks, $70 for a direct mount 1x crank (includes Hollowtech-type external BB and 30t chainring) available in sizes from 152mm. With 11-40t 9sp cassettes available, a 1x9 setup is affordable and simple.

Not in the same league as the Trailcraft cranks but less than half the price.


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## officeboy (Mar 28, 2012)

murrdogg11 said:


> https://spawncycles.com/brood-eldorado-syx-140
> 
> If anyone is curious the 155mm crank arms/spindle weighed in at 600g
> Bb is 110g without the spacers


That is without a chainring? So the Trailcraft are about 100g lighter?


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## jestep (Jul 23, 2004)

david.p said:


> While doing a build for my 12yo I came across these Suntour Zeron cranks, $70 for a direct mount 1x crank (includes Hollowtech-type external BB and 30t chainring) available in sizes from 152mm. With 11-40t 9sp cassettes available, a 1x9 setup is affordable and simple.
> 
> Not in the same league as the Trailcraft cranks but less than half the price.


Really sucks that the spectra 152mm is no longer available. It was like $35, under 600g for 1x, and fit on the typical square taper BB's that most kids bikes still come with without any modification.


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## GSJ1973 (May 8, 2011)

jestep said:


> Really sucks that the spectra 152mm is no longer available. It was like $35, under 600g for 1x, and fit on the typical square taper BB's that most kids bikes still come with without any modification.


Spectra same as Thorn cranks possibly? (not $35 but if local not a bad deal)

https://www.sjscycles.co.uk/cranks/150-thorn-10464-pcd-triple-crankset-mk2-black/?geoc=US


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## jestep (Jul 23, 2004)

GSJ1973 said:


> Spectra same as Thorn cranks possibly? (not $35 but if local not a bad deal)
> 
> https://www.sjscycles.co.uk/cranks/150-thorn-10464-pcd-triple-crankset-mk2-black/?geoc=US


Slightly different but that looks like a great option.


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## guaruska (Aug 3, 2017)

Totally agree with crankset length on kids bikes. Now daughters moving up in size and problem starts all over. 170mm cranks for a 147 cm (4'10") on the 27.5 xs...wouldn't think so. Looking for 160mm cranks hollowtech II, fruitless. Anybody knows? Except for Lightning in carbon - I don't even dare to ask price on those.

I do disagree with small chainring with wide range cassette. My youngest boys ride 20" mtbs with 125mm cranks, 11-42t cassette and 38t up front. They rarely use the lowest gear, only on technical uphills in the woods. On paved road the highest gear is not enough - they spin out, at around 45 kph.


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## thesmokingman (Jan 17, 2009)

guaruska said:


> Totally agree with crankset length on kids bikes. Now daughters moving up in size and problem starts all over. 170mm cranks for a 147 cm (4'10") on the 27.5 xs...wouldn't think so. Looking for 160mm cranks hollowtech II, fruitless. Anybody knows? Except for Lightning in carbon - I don't even dare to ask price on those.
> 
> I do disagree with small chainring with wide range cassette. My youngest boys ride 20" mtbs with 125mm cranks, 11-42t cassette and 38t up front. They rarely use the lowest gear, only on technical uphills in the woods. On paved road the highest gear is not enough - they spin out, at around 45 kph.


Check out the sram nx which comes in 155mm.


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## Steve-XtC (Feb 7, 2016)

thesmokingman said:


> Check out the sram nx which comes in 155mm.


Definitely.. at 155 the problem is easier solved. 
Don't worry about 5mm shorter than 'ideal' as opposed to 5mm too long.

If anyone is feeling flush, has just received a bonus, inhertitance or such it seems Hope now are selling their kids cranks they made for their own lease only fleet. 


> Designed specifically for children's bikes and their wee legs. Choose either 135mm or 150mm lengths. These cranks don't include a spider or chainring.


Around $200 + spider + chainring


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## guaruska (Aug 3, 2017)

Thanx for advice. I've read about the sram nx 155 in this thread. I would need a different bb for that (not sure?). And then the 2x chainrings. So I might as well ask about price for the Lightning crankset for the size I (my daughters) would be fit for.
Found the Bor xm557 165mm at roughly 600 usd. Kill to birds in one stone: lighter bike and lighter wallet! It's just annoying to sit on a thick wallet while commuting to work. It makes my hip crooked.

I also found Federleicht 160mm, but they only make them in 1x. Only 500 usd. Rider max weight 50kg. Hey...just like my wallet, in grams.


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## Steve-XtC (Feb 7, 2016)

Are you absolutely set on 2x? 
Unless you have long sections of road to link up I find it hard to find a need nowadays.
There are a few fire trails I spin out on 27.5 (depending on chain-ring) but not often enough or for long enough or I'd be going much faster .. to make me want to go back to 2x and I'm nowhere near maximum range possible today on any of my 27.5 bikes.

(Neither is jar but he's on 24" wheels)


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## guaruska (Aug 3, 2017)

I tried to convince them to go for 1x front but both wanted 2x. With four kids I've noticed their cadence is different from adults, and if they didn't make use of all the gearing it wouldn't be up to them to decide, but they make use of it.


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## thesmokingman (Jan 17, 2009)

Huh? You're gonna spend 600 bucks on a 2x crank for your kid????

Your kids asked for 2x??? What the?


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## guaruska (Aug 3, 2017)

Uhm. No, not gonna spend 600 bux on a crankset. I was being ironic.
No, they didn't ask for 2x. Bike has 2x and I asked them if they'd prefer 1x. They tried it on brothers bike and didn't like it.
And besides, even if the answer was the opposite, it would be my choice and not anybody elses problem. They do have killer bikes, but I build them with great deals I find on ebay or elsewhere.


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## thesmokingman (Jan 17, 2009)

guaruska said:


> Uhm. No, not gonna spend 600 bux on a crankset. I was being ironic.
> No, they didn't ask for 2x. Bike has 2x and I asked them if they'd prefer 1x. They tried it on brothers bike and didn't like it.
> And besides, even if the answer was the opposite, it would be my choice and not anybody elses problem. They do have killer bikes, but I build them with great deals I find on ebay or elsewhere.


Hehe, gotcha.

And on them preferring 2x, that is really surprising. Sequential shifting is logistically the easiest, granted if its the same total range. However using 2x or more, is not all that efficient because you lose some range in the process. Its also a pain in that when you hit that multi (change front ring) you get put out in a wrong gear and have to knowingly compensate. Thus its kind of surprising that the kids would prefer 2x.


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## guaruska (Aug 3, 2017)

Maybe surprising. Imho they use the 2x as intended: large chainring by default, granny when required on technical uphills. The young girl (12 y o, 138 cm 30 kg) has a road/mtb setup for the 2x, 40t and 34t with 11-36t cassette, on her 24er. It took her a little practice to get the point, but once the point made it through the use of it is easy as pi. The older (on the 27.5 with 170mm cranks) has 36t and 22t in front, 11-36t rear. She understands it perfectly without an explanation. But cranks are not ideal. She's 13 y o, 148 cm with 43 kg of muscles. Stronger than most boys in her class and with more stamina by far. A short ride round the neighborhood for us is at least 20-30km.
She was the only child in her class to make the gymclass challenge: hang from the 3 m platform (height from the water) with hands only, and climb back up. First girl in school history to make it. On her first day. (Can u tell I'm proud?)


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## Dr_UNIX (Jun 28, 2015)

murrdogg11 said:


> https://spawncycles.com/brood-eldorado-syx-140 If anyone is curious the 155mm crank arms...


Don't you mean 140mm? Both the URL and the actual webpage say 140mm. I cannot find any mention of 155m at spawncycles.com


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## Dr_UNIX (Jun 28, 2015)

MXIV424 said:


> Sram nx 155mm is claimed at 680g with 32t. Add 118g for bb for $30 and its 798g


Real weight for ours is
475g right arm + GXP spindle, w/32T + 4x CR bolts
229g left arm
2g pedal washers
706g out-the-door


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## Dr_UNIX (Jun 28, 2015)

david.p said:


> I came across these Suntour Zeron cranks, $70 for a direct mount 1x crank (includes Hollowtech-type external BB and 30t chainring


THANK-YOU! I've been searching far and wide for a 160mm two-piece crankset to up-size my (now 5'3") daughter's SRAM NX-155's.

I'd prefer something better quality than SR-Suntour; but this is only the second offering I've found.

If I were Steve-XtC in the UK, I'd be trying to buy the German VPACE 160mm at http://www.vpace.de/produkt/max-kinderkurbel/?attribute_laenge=160+mm for €129. But I cannot find any way to buy them in the USA.


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## Dr_UNIX (Jun 28, 2015)

guaruska said:


> (on the 27.5 with 170mm cranks) ... She's 13 y o, 148 cm with 43 kg of muscles


Good grief!! A 4'10", 95'lb person on *170mm* cranks?!? I ride 170mm cranks at 172cm tall.

Even 165mm are too long IMHO, but at least those should be SO EASY to source for use with your existing BB + chain rings there's no reason not to at least give her those.



> First girl in school history to make it. ... (Can u tell I'm proud?)


:thumbsup: :thumbsup: :thumbsup:


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## Dr_UNIX (Jun 28, 2015)

Acrophylos said:


> SRAM Rival with removable spider is easy to shorten


What did you shorten them to? Do you have pics of the finished product [from the back side]?


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## Dr_UNIX (Jun 28, 2015)

guaruska said:


> I also found Federleicht 160mm


Uggg, http://www.federleicht-bike.at/inde...kurbeln/federleicht-kurbelgarnitur-160-detail for 388€ ?? [US$448 before shipping, etc...] More than Double my budget for this.


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## thesmokingman (Jan 17, 2009)

?? Why do you think a 5'3 rider needs another 5mm?


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## guaruska (Aug 3, 2017)

Dr_UNIX said:


> If I were Steve-XtC in the UK, I'd be trying to buy the German VPACE 160mm at MAX Kinderkurbel - VPACE Bikes for €129. But I cannot find any way to buy them in the USA.


They ship them worldwide. Contact them for info on this. I know their website is in german only, but I did figure that part out. They answer in English, I've contacted them before. You'd probably be slaughtered with customs but if u can't get anything else...in that price range. U have the lightning cranks at a respectable cost of 740 usd, in Califas.


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## guaruska (Aug 3, 2017)

The difference is huge on shorter persons. My daughter on the 24" went from cruising speed of 15 kph to almost 25 when shortening cranks to ideal length (from 152mm to 140mm).


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## Dr_UNIX (Jun 28, 2015)

thesmokingman said:


> ?? Why do you think a 5'3 rider needs another 5mm?


A fair question. Based on how short she was when using 155mm/152mm cranks, the "look" of her pedaling, her typical cadence and gear she says she can push - I think 155mm is too short. Looking at 4-5 on-line guides, I also compute 160mm as the right crank size.

Also, anything shorter and that would seem to call into question the 170mm I use for road/CX/XC at 5' 7.5".

Determining Crank Length for Children
10% height: 160cm * 10% => 160mm

https://highpath.co.uk/crank-shortening/
effective leg length = 749mm => 749mm * 22% for child = 165mm
effective leg length = 749mm => 749mm * 20% for adult = 150mm

measured inside leg length = 75.9cm
Bicycle cranks: Check your Cranks!
inside leg length 66 to 70cm : 155mm
inside leg length 72 to 75cm : 160mm
inside leg length 75 to 78cm : 162.5mm

Bicycle Crank Length
2.16 * 75.9cm = 163.9mm


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## ladljon (Nov 30, 2011)

*Short cranks*

5' 28" inseam...went from 170/165mm to 125/135mm never go back...wished I did this 20yrs ago.


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## Steve-XtC (Feb 7, 2016)

> If I were Steve-XtC in the UK, I'd be trying to buy ....


When we needed the them it was just quicker and easier to make them from existing cranks. 
Having done it once .. it's much easier than I'd expected.


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## thesmokingman (Jan 17, 2009)

Dr_UNIX said:


> A fair question. Based on how short she was when using 155mm/152mm cranks, the "look" of her pedaling, her typical cadence and gear she says she can push - I think 155mm is too short. Looking at 4-5 on-line guides, I also compute 160mm as the right crank size.
> 
> Also, anything shorter and that would seem to call into question the 170mm I use for road/CX/XC at 5' 7.5".
> 
> ...


Most of those links are all based on assumptions. There's no science in their science. Studies have shown that the formulas are wrong, all wrong. There is actually no appreciable difference in power output from 130mm to 190mm crank lengths.

Did you read your first link? And yet you are planing to upsize cranks by 5mm? Moving up 5mm is just throwing money away imo. How I judge crank length is not longer is better or even longer as the goal. Instead its how the hips of the rider vs their knee's top dead center. If the rider has to rock or drop their hip to complete a pedal rotation, then that needs to be looked at. That said, if I were you would not be wasting money on cranks.



> OTOH a lot of testing and real world examples show that you can go considerably shorter than this length with no loss of power. This is because your knees are straighter so you can push harder on the pedals. And because your muscles are in the length range where they can apply peak tension through more of the circle (I list a few examples below.)





> So, as a child grows to a height where they COULD ride longer cranks, they aren't giving up anything by riding the cranks that were fine for them a year or two ago. On the other hand a child riding cranks sized for the height he or she will be in a couple of years will not only be slower but also risks knee injury. About 15% of my customers have damaged their knees riding cranks that were too long.


Moving on...



> One of my customers, 5'-7" (170cm) tall professional triathlete Courtney Ogden, won the big money 2011 Western Australia Ironman on 145s. The next day, despite being wasted, he ordered a set of 130s. He's done extensive work with the people at PowerCranks where they are becoming big advocates of shorter cranks.


A better introductory to crank length is Cervelo's take on the study...



> But for each of these pros, *the change to a shorter crank solved a range of motion issue at the hip that allowed them to comfortably make other changes to reduce aero drag without decreasing power.*


https://www.cervelo.com/en/engineering-field-notes/a-new-spin-on-crank-length


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## jochribs (Nov 12, 2009)

Awesome post Smoking. The mindset of Dr. Unix (no offense meant personally), is why we have such limited options for varying crank lengths. Companies have little reason to produce shorter options because end users and bike companies (that should straight up know better) will buy the longest ones they can anyway.


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## svinyard (Aug 14, 2017)

Good info smoke. Helps alot!


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## MXIV424 (May 30, 2018)

Dr_UNIX said:


> Real weight for ours is
> 475g right arm + GXP spindle, w/32T + 4x CR bolts
> 229g left arm
> 2g pedal washers
> 706g out-the-door


Then a bb around 100-120 grams puts it at the 800 mark, correct?



thesmokingman said:


> A better introductory to crank length is Cervelo's take on the study...
> 
> https://www.cervelo.com/en/engineering-field-notes/a-new-spin-on-crank-length


Good read, thanks.


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## Eneen (Jul 4, 2017)

I think best is to 0.21 to 0.216 x inseam, have to find source for this though (here it is as 20-22% https://highpath.co.uk/crank-shortening/). This will give about 102-105mm cranks for my 6yo daughter (current 127mm is insane) and completely out of luck finding proper cranks. There is prowheel 102mm in author bicycles but it's not available as oem. I'm thinking about converting some road crank as they tend to have lower q-factor, any suggestions?


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## guaruska (Aug 3, 2017)

There are cheap 105mm on ebay. Steel cranks with 30t chainring. I also think hollandbike has some of that size. Here: https://www.ebay.co.uk/itm/CHILDS-B...h=item5b4e89eb1f:g:iEsAAOSwv0tVbyXT:rk:1:pf:0

And some really expensive to pick your own chainring: https://www.ebay.co.uk/itm/Von-Soth...h=item1edf694ac2:g:qRMAAOSwozxa4B40:rk:3:pf:0


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## guaruska (Aug 3, 2017)

Eneen said:


> I think best is to 0.21 to 0.216 x inseam, have to find source for this though (here it is as 20-22% https://highpath.co.uk/crank-shortening/). This will give about 102-105mm cranks for my 6yo daughter (current 127mm is insane) and completely out of luck finding proper cranks. There is prowheel 102mm in author bicycles but it's not available as oem. I'm thinking about converting some road crank as they tend to have lower q-factor, any suggestions?


And here: https://www.ridewill.it/c3/en/cycling/1/drivetrain/3/cranksets/770/cranksets-mtb/37/


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## Feldybikes (Feb 17, 2004)

Spawn sells 102mm cranks for $50. They even go down to 89mm if you'd want that:

https://spawncycles.com/spawn-cycles-alloy-cranks-102mm


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## RMCDan (Feb 28, 2008)

guaruska said:


> And some really expensive to pick your own chainring: https://www.ebay.co.uk/itm/Von-Soth...h=item1edf694ac2:g:qRMAAOSwozxa4B40:rk:3:pf:0


Wow, 230 grams.

I'll second the Spawn recommendation, assuming were talking square taper. If 2-piece thru-axle are needed, then get the 115s Flow sells (not on their website, I've been told you can email them and they'll sell you a set).


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## Acrophylos (Jun 10, 2018)

Eneen said:


> I'm thinking about converting some road crank as they tend to have lower q-factor, any suggestions?


See my post from June (same thread). Shortening SRAM Rival with removable spider is very easy to shorten if you have a drill press and the pair of thread taps. Considering that we're talking about kids, presumably under 110lbs / 50kgs strength really isn't a concern.

My son has been riding the shortened 115mm Rival cranks on his Flow Kids Bike for ~5 months and I'm very happy with the result.

Feel free to PM me if you have questions.


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## Acrophylos (Jun 10, 2018)

RMCDan said:


> If 2-piece thru-axle are needed, then get the 115s Flow sells (not on their website, I've been told you can email them and they'll sell you a set).


The Flow cranks are cut down MTB cranks with 175mm Q factor. I have a set that I would be happy to sell, PM me if interested.

IMHO cutting down SRAM Rival is a better solution, yielding 150mm Q factor but it takes a bit of work as the backside of the crank needs to be tapered to clear chainstays (and won't work on some bikes).


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## Eneen (Jul 4, 2017)

Thank you guys!
Spawn are really nice, though seem not to be available in EU, need to ask them if they can send directly.
My daughter owns spec riprock 20 and original cranks have Q=172 and L=127. There's about 8mm of free space to chainstays each side so I can assume that Q=162 is save option here. BB is 68, and axis length 118 and I've got spare 107mm UN72. Chainline is awfully moved to smaller cogs, need to think about this but indeed road cranks may be option here. However take a look at these:
https://www.bike-project.pl/pl/p/Korby-STURMEY-ARCHER-FCS720-42T/1124
They are using cranks from sunrace except they are 104:
https://http2.mlstatic.com/pedivela...mm-D_NQ_NP_997036-MLB25586167236_052017-F.jpg
This is nice as I can buy two and make 4 holes every 20mm and swap. And it uses BCD104 so oval NW is way to go.
Need to ask dealer what's depth of recession, will let you know.

BTW, spec cranks are about 520g


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## Acrophylos (Jun 10, 2018)

*Shortened SRAM Rival Cranks*

@Dr_UNIX [What did you shorten them to? Do you have pics of the finished product [from the back side]?]

Sorry I didn't see your post sooner...here's a closeup pic of the left and right crank arm ends. Note that I tapered the backside to clear the chainstay.

I used a drill press to punch the hole, tapped the threads by hand, then cut the arms. Using a belt sander I shaped the ends, and finally finished with a rasp to fine-tune things.


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## igormskru (Nov 29, 2018)

What is the q factor on 
Trailcraft direct mount cranks?
Vpace makes goog short direct mount cranks, but with a 167mm q factor. That's too much.

A 20 inch Woombike has a 130 q factor on 110mm cranks (square taper with the shortest spindle shimano makes) and for the next bike i'm searching for 130-140mm cranks with a 130-140 (150 at most) q factor


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## Ötzi (Sep 20, 2004)

152mm Suntour Zeron 30t $59.46 shipped from Suntour with 15% coupon and free shipping. 

Steel chainring definitely doesn’t help the weight. For the price it’s okay but chainring mounting is proprietary. The smallest replacement is a 30t and the aluminum rings cost almost as much as this entire crankset.


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## svinyard (Aug 14, 2017)

I think TrailCraft is now selling 127mm, 140mm, 152mm & 165mm direct mount crankset with BB and your choice of chainring down to 26t for 160$. Pretty awesome

https://www.trailcraftcycles.com/product/trailcraft-direct-mount-cranks/

Pretty awesome weight savings for the money!
Lengths Available: 127mm, 140mm, 152mm 24mm 7050 ALLOY Spindle 51mm Chainline, 168mm Q-Factor

140mm with 30t - 558g including BB 
152mm with 30t - 582g including BB


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## guaruska (Aug 3, 2017)

svinyard said:


> I think TrailCraft is now selling 127mm, 140mm, 152mm & 165mm direct mount crankset with BB and your choice of chainring down to 26t for 160$. Pretty awesome
> 
> https://www.trailcraftcycles.com/product/trailcraft-direct-mount-cranks/
> 
> ...


There are Babyracing cranksets, from Italy. Square taper 110 bcd. In alu. Lightweight. They have in sizes 125, 140, 155 and 165 on ebay. They used to have more sizes, such as 130 and 135 also, maybe they're not made anymore. Quite cheap too, comparing to others. Some 27 euros for the set w/o bb. Shipping will cost though. There are some italian stores online that sells them too. I think they're 2x.

There's also Sugino square taper 110 bcd, 152mm. They come in 1x, 2x or even 3x. Little more expensive than baby racing, but come in black (except the 3x) or natural.


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## jestep (Jul 23, 2004)

guaruska said:


> There are Babyracing cranksets, from Italy. Square taper 110 bcd. In alu. Lightweight. They have in sizes 125, 140, 155 and 165 on ebay. They used to have more sizes, such as 130 and 135 also, maybe they're not made anymore. Quite cheap too, comparing to others. Some 27 euros for the set w/o bb. Shipping will cost though. There are some italian stores online that sells them too. I think they're 2x.
> 
> There's also Sugino square taper 110 bcd, 152mm. They come in 1x, 2x or even 3x. Little more expensive than baby racing, but come in black (except the 3x) or natural.


I think you're referring to their previous 1x crank. These DM ones use a 24mm spindle.


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## TimTucker (Nov 9, 2011)

igormskru said:


> What is the q factor on
> Trailcraft direct mount cranks?
> Vpace makes goog short direct mount cranks, but with a 167mm q factor. That's too much.
> 
> A 20 inch Woombike has a 130 q factor on 110mm cranks (square taper with the shortest spindle shimano makes) and for the next bike i'm searching for 130-140mm cranks with a 130-140 (150 at most) q factor


Just emailed Trailcraft and they responded a few minutes later that the q factor is 168mm for the 152mm direct mount cranks.


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## dookie (Sep 6, 2005)

I just replaced the OEM Trailcraft square-taper 152mm (on a Pineridge I recently picked up used) with the Flow external-cup 135mm . Here's what I learned...

The Flow stuff is all made by Lasco...arms and BB. Crankset weighs 635g complete (30t RaceFace NW & bolts, preload bolt), BB 120g (with all spacers) = 755g. Typical mtb Q-factor (170mm +/-).

The Trailcraft frame uses a 68mm shell (unfaced/unchased at original assembly but corrected before new BB went in...come on guys! Brake bosses also unfaced). Arms are also Lasco, BB by Neco. Crankset weighs 540g (same ring/bolts), BB 275g = 815g. Typical mtb Q-factor (and very little room to shorten spindle). All into the cabinet for him to grow into...


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## Eneen (Jul 4, 2017)

Working on 3D printed crankset. Q-factor 150 or less (depends on frame), BCD 104, 110mm, about 400g without chainring. Up to 30kg. Let you know if prototype survives my 65kg


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## Gangly1 (Jul 5, 2016)

Eneen said:


> Working on 3D printed crankset. Q-factor 150 or less (depends on frame), BCD 104, 110mm, about 400g without chainring. Up to 30kg. Let you know if prototype survives my 65kg


Cool project - square taper cranks? Fairly heavy, but they look cool, almost like DXRs or Saints.


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## Eneen (Jul 4, 2017)

Thx!
Yep, square, due to compatability. They are empty inside, so I can make thinner wall, no problem, but problem is with pedal thread, there's weak spot there. Feeling like I will need aluminium plate and additional M16 thread to fix this, but will see...


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## Gangly1 (Jul 5, 2016)

What is the material, aluminum? Can you just make the end solid and then tap in the pedal threads or use a helacoil?


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## TimTucker (Nov 9, 2011)

Eneen said:


> Working on 3D printed crankset. Q-factor 150 or less (depends on frame), BCD 104, 110mm, about 400g without chainring. Up to 30kg. Let you know if prototype survives my 65kg


Looks like an interesting experiment -- would there be much point / weight savings in integrating the chain ring as part of the design?

Was looking at this YouTube channel with a guy who plays around with 3d printing bmx parts (including a sprocket) and it made me wonder:


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## Eneen (Jul 4, 2017)

I've designed them to be PLA, they need to be cheap. Yeah, helacoil is what I'm thinking about, but need to get pair first. However will test without and will see how that works. Helacoil has external M16 thread and will surely reinforce pedal mount due to larger diameter.


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## Eneen (Jul 4, 2017)

TimTucker said:


> Looks like an interesting experiment -- would there be much point / weight savings in integrating the chain ring as part of the design?
> 
> Was looking at this YouTube channel with a guy who plays around with 3d printing bmx parts (including a sprocket) and it made me wonder:


Not sure now, I drew them yesterday, so it's really fresh 
Draft is currently printing, after everything fits I will print full sample and test it.

WOW this sprocket is really great, if this is possible I will surely integrate oval one.


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## TimTucker (Nov 9, 2011)

Eneen said:


> Thx!
> Yep, square, due to compatability. They are empty inside, so I can make thinner wall, no problem, but problem is with pedal thread, there's weak spot there. Feeling like I will need aluminium plate and additional M16 thread to fix this, but will see...


If you want to go really deep down the rabbit hole of custom designs, you could try an approach to pedal design like this (bearings for the pedal embedded in the crank itself):
https://www.bikeradar.com/us/gear/c...ew-momentum-bicycle-flypaper-pedals-09-34550/
https://forums.mtbr.com/downhill-fr...hootout-best-flat-607155-16.html#post11495303


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## Eneen (Jul 4, 2017)

Damn square taper, diameter is so small... I need metal adapter from taper to something bigger due to plastic plasticity... Even 24mm shimano spindle seems too small...

EDIT: Ok, decided to do 24mm spindle mount. It will take a while to redesign this, but first need to do pedal mount stress testing.


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## Eneen (Jul 4, 2017)

In the meantime take a look:
https://www.aliexpress.com/item/Bicycle-Crank-5-Nail-BCD-110-Aluminum-Alloy-Crankset-Length-152mm-Bike-Parts-BMX-Folding-Bike/32786260678.htmlSeems really nice shortening candidate.


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## TimTucker (Nov 9, 2011)

Eneen said:


> In the meantime take a look:
> https://www.aliexpress.com/item/Bicycle-Crank-5-Nail-BCD-110-Aluminum-Alloy-Crankset-Length-152mm-Bike-Parts-BMX-Folding-Bike/32786260678.htmlSeems really nice shortening candidate.


110BCD is the main downside I see to those, since that limits you to 33T chainrings at minimum.

If you're feeling really adventurous, I suppose there may be enough material there to drill & tap for 74BCD.

If you're OK with 110 chainrings, the Sinz Expert cranks are pretty similarly priced and go down to at least 120mm:
https://www.ebay.com/sch/i.html?_fr...t=0&_odkw=sinz+expert&LH_BIN=1&LH_TitleDesc=0


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## MXIV424 (May 30, 2018)

Dm is really where it’s at. The ability to throw a 26 or 28t ring on there makes it perfect for a kids bike.


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## TimTucker (Nov 9, 2011)

MXIV424 said:


> Dm is really where it's at. The ability to throw a 26 or 28t ring on there makes it perfect for a kids bike.


If you've got 64BCD you can still go down to 22T or 24T narrow-wide pretty cheap (at 74BCD, i.e., old triple chainrings, you can go down to 24T or 26T):
https://usamade.myshopify.com/collections/sharktooth-pro-64mm-74mm

As a point of reference, I have the Trailcraft 152mm DM cranks on my MTB and a set of Suntour Jr 152mm cranks run as 1x7 w/ a 24T 64BCD chainring on an old Trek I use for pavement rides / pulling a bike trailer.

Both work well -- the Trailcraft is certainly lighter, but the Suntour + narrow-wide ring was a great cheap way to test to see if I'd like shorter cranks.


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## robscaff (Jan 5, 2019)

shortened xtr cranks 175mm down to 152mm


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## TimoA (Dec 22, 2014)

Found these pretty affordable Miranda branded alloy/steel 127mm 32T cranks. Supposedly they would be at least somewhat lighter than the all-steel 36T Prowheel cranks (900g) we have now but can't find any weight data. Does anyone recognize these being sold or used under any other brand? https://fahrradtopshop.de/epages/72...d425cc/Products/"A550.832.291/9"&Locale=de_DE

Granted they would not be a huge investment even if they weren't that light but the pretty steep delivery costs would make it an extra bummer.


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## backinmysaddle (Jul 27, 2011)

It looks like the shorter suntours are out of stock now and when i price out thr 152 NX vs 152 Trailcraft, there isnt a ton of price difference as the Trailcraft comes w the BB and chainring size of my choice whereas NX has no BB and I’d want to move to a 30t ring.


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## Eneen (Jul 4, 2017)

In the meantime:
https://www.aliexpress.com/item/Pro...-kids-chlid-bike-chain-wheel/32951019209.html
Must haven ended recently but maybe possible to ask seller.


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## backinmysaddle (Jul 27, 2011)

Suntour 152mm back in stock, grabbed a pair for my daughter’s new xs 29er hardtail i built up. Firstorder code takes 15% off.


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## backinmysaddle (Jul 27, 2011)

backinmysaddle said:


> Suntour 152mm back in stock, grabbed a pair for my daughter's new xs 29er hardtail i built up. Firstorder code takes 15% off.


The chainline blows on these things. I had several longer 1x cranksets on and had no problem w backpedal issues. These are a solid 10mm off in chainline from other cranks. Drops to 3rd gear when back pedaling.


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## TimTucker (Nov 9, 2011)

backinmysaddle said:


> The chainline blows on these things. I had several longer 1x cranksets on and had no problem w backpedal issues. These are a solid 10mm off in chainline from other cranks. Drops to 3rd gear when back pedaling.


Just went out and measured the one I have on my around town bike: looked pretty close to 48mm chainline on the small ring. I'm running it as a 1x7 with a 64bcd narrow wide ring, so it actually works out really well.


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## 53sled (Mar 11, 2016)

backinmysaddle said:


> The chainline blows on these things. I had several longer 1x cranksets on and had no problem w backpedal issues. These are a solid 10mm off in chainline from other cranks. Drops to 3rd gear when back pedaling.


Are you referring to the square taper triple cranks that are $30 on ebay or the zeron 2 piece cranks?
https://www.srsuntour.us/collections/cranks/products/zeron-1-x?variant=45338041742


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## TimTucker (Nov 9, 2011)

53sled said:


> Are you referring to the square taper triple cranks that are $30 on ebay or the zeron 2 piece cranks?
> https://www.srsuntour.us/collections/cranks/products/zeron-1-x?variant=45338041742


In my case, the $30 square taper triple cranks.

47.5mm to the middle ring is pretty standard for square taper, so if you were expecting to run as 1x using the middle ring, I could see how it might cause problems.

If you're planning to run 1x using the 64BCD small position, it works out OK.


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## rabitoblanco (Feb 21, 2017)

So here's a different thought on crank length-- I know that (is it Sheldon? is it BikeSmith?) whomever started the conversation on this is talking about _seated_ pedaling. 
I watch 6yr old Rowan {edit: he is 4'6"} riding standing (on 160mm), and I can see he is swaying his hips/ body all the way down one way, and then swinging to the other side. So I feel a shorter crank would be useful.

Then I think about how much faster he'd have to spin his legs-- and I wonder, will a shorter crank be detrimental to riding standing? Or does it just mean that I can continue to stay away from the dinner-plates on the back wheel?


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## ladljon (Nov 30, 2011)

rabitoblanco said:


> So here's a different thought on crank length-- I know that (is it Sheldon? is it BikeSmith?) whomever started the conversation on this is talking about _seated_ pedaling.
> I watch 6yr old Rowan riding standing (on 160mm), and I can see he is swaying his hips/ body all the way down one way, and then swinging to the other side. So I feel a shorter crank would be useful.
> 
> Then I think about how much faster he'd have to spin his legs-- and I wonder, will a shorter crank be detrimental to riding standing? Or does it just mean that I can continue to stay away from the dinner-plates on the back wheel?


Just shift to a harder gear and spin slower....I'm on 135mm


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## jochribs (Nov 12, 2009)

rabitoblanco said:


> So here's a different thought on crank length-- I know that (is it Sheldon? is it BikeSmith?) whomever started the conversation on this is talking about _seated_ pedaling.
> I watch 6yr old Rowan riding standing (on 160mm), and I can see he is swaying his hips/ body all the way down one way, and then swinging to the other side. So I feel a shorter crank would be useful.
> 
> Then I think about how much faster he'd have to spin his legs-- and I wonder, will a shorter crank be detrimental to riding standing? Or does it just mean that I can continue to stay away from the dinner-plates on the back wheel?


In my experience on bikes and putting in lots of miles for a number of years, you shouldn't worry about increased cadence due to the tighter circle. And actually, the cadence won't really be increased for the same given gear.

Think about it. A clock hand or a windmill blade is moving faster at its tips than it is moving the further down the hand/blade you go for a given revolution speed.

You have seen it for yourself, the cranks are grossly too long, and it's throwing off his physical mechanics. There is virtually no good reason to push long cranks. We actually make power better on shorter ones. At 6, I'm going to throw out a guess that 125-130 would be better for him, without actually seeing his size. The circles he will be pedaling will be functionally better for his leg length, his joints will not be getting strained, the saddle height will be able to come up for better leg extenxion since he won't need to reach nearly as low for the bottom of the stroke.


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## Steve-XtC (Feb 7, 2016)

rabitoblanco said:


> So here's a different thought on crank length-- I know that (is it Sheldon? is it BikeSmith?) whomever started the conversation on this is talking about _seated_ pedaling.
> I watch 6yr old Rowan riding standing (on 160mm), and I can see he is swaying his hips/ body all the way down one way, and then swinging to the other side. So I feel a shorter crank would be useful.
> 
> Then I think about how much faster he'd have to spin his legs-- and I wonder, will a shorter crank be detrimental to riding standing? Or does it just mean that I can continue to stay away from the dinner-plates on the back wheel?


I think chrisjobs already covered this but he is still making the same revolutions on every gear his feet just don't travel the same distance. 
If he was pedalling efficiently which by your description he isn't then for 130 cranks he would have a tiny amount of less leverage (130/160) delivered on the downstroke ... but he isn't pedalling efficiently and he is basically reducing the part where he can put power down to a very small arc by moving his weight over the pedal.

At the same time he's more or less missing being able to put power down in the larger part of the downstroke ... and moving his whole body over to do this.


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## TimTucker (Nov 9, 2011)

Even if the efficiency were the same, gaining over 1" greater ground clearance on a kid's bike with an already low BB is nothing to scoff at.

Here's a perspective from one BMX company on why shorter cranks may be just as useful for standing:
https://www.profileracing.com/tech-tip-2-crank-it-down/


> 1. Shorter cranks allow you to bunny hop higher. As a simple experiment, try jumping with your feet spread apart, then try with your feet closer together (as if being in a position for pedaling). You can always jump higher with your feet closer together.
> 2. Ambidextrous spinning: It's much easier to 180 (360, 540 etc&#8230 both ways with your feet closer together.
> 3. Lighter weight: The shorter the crank, the less steel used in its tubular construction.
> 4. More rigid/less flex: Shorter cranks should, in theory, last longer over time because there's less leverage put upon them.


From the various BMX forums where I've looked into this, the general consensus seems to be that techniques like manuals are also easier on shorter cranks -- which could translate into quicker skills development for kids.


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## Gangly1 (Jul 5, 2016)

BMX racers are very serious with their crank lengths. My boys race, and there is a good crank length formula/ calculator that I use for them at https://heliumbikes.com/tech-articles

The formula is just inseam/0.173. Make sure to measure the inseam with their shoes on and use the method on the site. Of course there is still a bit of trial and error, but it gives you a good place to start with.


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## svinyard (Aug 14, 2017)

Gangly1 said:


> BMX racers are very serious with their crank lengths. My boys race, and there is a good crank length formula/ calculator that I use for them at https://heliumbikes.com/tech-articles
> 
> The formula is just inseam/0.173. Make sure to measure the inseam with their shoes on and use the method on the site. Of course there is still a bit of trial and error, but it gives you a good place to start with.


THAT looks good!

When my little guy got his Yoji 16"...his inseam was like 15.5. The 102mm cranks (I think) were EASILY too long and I swapped them for 95mm. Instantly better.

When I run that against your calculator iits pretty close.

My 51" 7yro has a 22in inseam. That works out to 124mm cranks. He is on 127mm on his Spawn Yama Jama 20". Those crank have worked well for him over the last couple of seasons. I'm working on getting him on a 24" bike with 140mm cranks. (most stock crank are 152 or 155 tho...). It all seems long.

I don't understand the differences between MTB and BMX Racing but I'm guessing its not drastic. Interesting.


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## rabitoblanco (Feb 21, 2017)

Thanks for a bunch of great responses. So shorter cranks it is--upgrade wheels later. Also a point about clearance I hadn't thought about. I was riding behind him yesterday and saw a spark as he hit something getting out of a turn--fun to see, but obviously undesirable, haha

@jochribs your guess is right on-- at 4'6", given the calculator above I come up with exactly that range for him.

This is what's on the Specialized FSR 24 now: 
Crankset: Truvativ ISO Flow, alloy 160mm with replaceable chainrings and capless bo, Truvativ 42t 7075alloy, heat treated Cr-Mo 32t and 22t teeth
Bottom Bracket: TruVativ LE, 113mm spindle
BB Shell Width: 68mm English

Will the Spawn 127 fit directly over the existing square-tapered BB? Or is there a chainline issue I need to solve?

https://spawncycles.com/spawn-cycles-alloy-cranks-127
For $60 this would be a lovely move forward--but is there something about chainlines I need to watch out for?


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## jochribs (Nov 12, 2009)

rabitoblanco said:


> Thanks for a bunch of great responses. So shorter cranks it is--upgrade wheels later. Also a point about clearance I hadn't thought about. I was riding behind him yesterday and saw a spark as he hit something getting out of a turn--fun to see, but obviously undesirable, haha
> 
> @jochribs your guess is right on-- at 4'6", given the calculator above I come up with exactly that range for him.
> 
> ...


Make sure the taper style is the same. It will effect how far the cranks need to pull onto the BB in order to tighten. There's JIS and I forget the other one (I should know this, I was a wrench for years) Anyway, it probably is fine. I'll look it up.


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## TimTucker (Nov 9, 2011)

rabitoblanco said:


> Thanks for a bunch of great responses. So shorter cranks it is--upgrade wheels later. Also a point about clearance I hadn't thought about. I was riding behind him yesterday and saw a spark as he hit something getting out of a turn--fun to see, but obviously undesirable, haha


If the shorter cranks aren't enough to solve pedal strikes on turns, you could also look into narrower pedals (depending on how wide his feet are). So far we've tried Tioga Dazz Lites (nice, relatively cheap nylon option) and some Kactus pedals from aliexpress (super light metal, but needs different pins to be usable).


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## jochribs (Nov 12, 2009)

So Spawn doesn't say anything about the taper style other than use them with "standard square taper" which is pretty much JIS, of which the Truvativ BB you have is as well, so I'd say giddy up.


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## Cerpss (Sep 13, 2015)

If I switched to something like the Answer cranks that use an ISO taper would I need to use a longer/shorter spindle than what's in a JIS taper bottom bracket? Not sure if the length difference is built into cranks or if I'd need to account for it in the new bottom bracket. And being the spindle sets the Q factor I'd assume the crank arms should clear the chainstay as long as i keep the crank arm length the same or shorter?


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## carlhulit (Sep 13, 2005)

Looking at the 16" commencal ramones, it has 114mm steel cranks, seems like it would be possible to drill a second set of holes for ~95mm, then tap with 1/2-20. Any reason not to do this?


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## jochribs (Nov 12, 2009)

https://www.sheldonbrown.com/bbtaper.html

This does a pretty good job of describing the difference and when and how you can mix them. With and ISO crank, you will need a shorter JIS BB to have the right chainline. At that point, if you are needing a different BB, just get an ISO (Answer) BB. My thought anyway.


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## jochribs (Nov 12, 2009)

carlhulit said:


> Looking at the 16" commencal ramones, it has 114mm steel cranks, seems like it would be possible to drill a second set of holes for ~95mm, then tap with 1/2-20. Any reason not to do this?


Opinions might vary, but my view is that I wouldn't. It would probably be fine though. I'd sooner get my hands on some aluminum take-offs from another bike and hack them down.

I actually have a set from my sons Raleigh RX24 if you want them.


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## rabitoblanco (Feb 21, 2017)

jochribs said:


> So Spawn doesn't say anything about the taper style other than use them with "standard square taper" which is pretty much JIS, of which the Truvativ BB you have is as well, so I'd say giddy up.


Talk about analysis paralysis--just as I was about to get those, I came across the from Flow : 
Is the weight reduction from the threaded BB (vs. existing UN-55) worth exchanging for a 7mm longer crank(127mm Spawn vs 135)?

https:///product-page/flow-crankset
"2 piece system with 68mm threaded bottom bracket
135mm arm length."

Sent from my Pixel using Tapatalk


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## jochribs (Nov 12, 2009)

rabitoblanco said:


> Talk about analysis paralysis--just as I was about to get those, I came across the from Flow :
> Is the weight reduction from the threaded BB (vs. existing UN-55) worth exchanging for a 7mm longer crank(127mm Spawn vs 135)?
> 
> https:///product-page/flow-crankset
> ...


I think it's better to get the best length, probably the 127's. You can always get a lighter BB.


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## Steve-XtC (Feb 7, 2016)

My 4’ 8.5” 9yr old is on 142mm cranks. 
Get the right length


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## rabitoblanco (Feb 21, 2017)

Thanks x2! 

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## Steve-XtC (Feb 7, 2016)

The other thing worth mentioning is square taper has loads of disadvantages but other than weight they don’t really apply to kids. It’s not like they will be complaining the BB isn’t stiff enough when they lay down 500W

It also has advantages... you can easily change the chain line and new BBS are cheap.
You can get a Shimano UN55 <<$20 

Weight wise I cut down some Shimano Zee (not the lightest) and some SRAM S600’s ($40?) to the same length and stuck everything on the scale and the Zee + External bb were 12g lighter than the SRAM and UN55.

Like 12g that’s a tire valve or bit of mud... obviously won’t be exactly the same for you but the point is it’s not a huge weight saving vs getting the right length, chainline etc.


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## GSJ1973 (May 8, 2011)

Gangly1 said:


> BMX racers are very serious with their crank lengths. My boys race, and there is a good crank length formula/ calculator that I use for them at https://heliumbikes.com/tech-articles
> 
> The formula is just inseam/0.173. Make sure to measure the inseam with their shoes on and use the method on the site. Of course there is still a bit of trial and error, but it gives you a good place to start with.


One thing to remember though is BMX is a sprint for a very short time and they never sit. Its been mentioned they typically go a bit longer for this reason.

Sitting to pedal over longer distances might be exact opposite of this formula, but I am no expert. High knees is typically the dead givaway when pedaling.


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## svinyard (Aug 14, 2017)

GSJ1973 said:


> One thing to remember though is BMX is a sprint for a very short time and they never sit. Its been mentioned they typically go a bit longer for this reason.
> 
> Sitting to pedal over longer distances might be exact opposite of this formula, but I am no expert. High knees is typically the dead givaway when pedaling.


We don't BMX race so I can't speak to that BUT this particular calculator is dumping out values that close to what mtb are using for kids or a fair bit below. So too long is def not an issue with this calculator at least.

This is really interesting too because kid cranks are a pain in the ass. Not only are our kids growing so we put them a bit early on a bike so they get more than one season on it... And the cranks are always a bit long. Secondly even the short-ish cranks are still really close to the ground for pedal strikes due to their tiny bikes and wheels.

So with this calculator pointing to us using even smaller cranks, it might be the best of both worlds and solve the sizing/high knees BS and make the bike a bit safer from pedal strikes (which happens in some chunky stuff).

My questions: how widely accepted is this site within the BMX world? Is there any downside to having cranks slightly too small?

My 51" 7yro is moving to a 24" bike and this calculator indicates he should be on cranks around 125mm rather than the stock 155 or Trailcraft style 140mm. That's a big drop. I'm happy to accept that but curious as to what others would think.


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## Eneen (Jul 4, 2017)

My 6yo has inseam of about 52cm and 114mm cranks. She says they are just perfect, much better then stock 127mm. Now she spins much faster. As I've written before, 0.2 x inseam seems to be sweet spot. I'm currently using 165mm having 82cm inseam and they are ok for me, much better then 175 or even 170. I've tried 152mm shortened xt cranks that my wife uses and they are fine too, I don't feel that they are too short or something. In general shorter cranks are better for geared bikes. They save knees and force you to use bit higher cadence.


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## TimTucker (Nov 9, 2011)

I've come across thaf bmx formula in the past too. Having looked at most of the studies with adults on crank length, there's really almost no downside to shorter cranks.

Thr one caveat for kids bikes is that moving to shorter cranks usually requires the saddle slightly higher for pedaling while seated, which could pose an issue for standover for a kid just starting out.

The flipside of that is that once kids are comfortable with a bike where the saddle is higher than their inseam it could help give a little more height for running a dropper.

I'm 5'10" and running 152mm cranks now.


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## jochribs (Nov 12, 2009)

svinyard said:


> My 51" 7yro is moving to a 24" bike and this calculator indicates he should be on cranks around 125mm rather than the stock 155 or Trailcraft style 140mm. That's a big drop. I'm happy to accept that but curious as to what others would think.


I had my guy on 120's on his 20". Cut down from the 160's that came on it. Insane how long they were.

I need to check out this calculator and see what it says about his crank length. I've just been doing a comparative percentage to my legs on 175's vs. his legs length and it's given me 135. However, who's to say that 175 is actually right for me?


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## Eneen (Jul 4, 2017)

What's your inseam?


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## svinyard (Aug 14, 2017)

jochribs said:


> I had my guy on 120's on his 20". Cut down from the 160's that came on it. Insane how long they were.
> 
> I need to check out this calculator and see what it says about his crank length. I've just been doing a comparative percentage to my legs on 175's vs. his legs length and it's given me 135. However, who's to say that 175 is actually right for me?


I have a 34"/86.3cm inseam and am also on 175. I rode 170's the other day on that Ripmo and it was fine. Maybe 165 would be too?

Regardless, at this point I might be able to take my 7yro 127mm cranks on his 20" Yama Jama and just put them on the kids next 24" bike and be good to go.

OR if the next bike comes with SRAM 155mm...I just cut them down to 130mm? I've never done that but there is a good machine shop here in town. I'd like to not have to drop a bunch of cash on new cranks/BB for a new bike.


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## jochribs (Nov 12, 2009)

Exactly, I have some decent cranks that were take offs on my bikes (switching from Sram to Shimano) that I can use too.


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## TimTucker (Nov 9, 2011)

svinyard said:


> I have a 34"/86.3cm inseam and am also on 175. I rode 170's the other day on that Ripmo and it was fine. Maybe 165 would be too?
> 
> Regardless, at this point I might be able to take my 7yro 127mm cranks on his 20" Yama Jama and just put them on the kids next 24" bike and be good to go.
> 
> OR if the next bike comes with SRAM 155mm...I just cut them down to 130mm? I've never done that but there is a good machine shop here in town. I'd like to not have to drop a bunch of cash on new cranks/BB for a new bike.


If his next bike comes with 155s, just keep him on the 127s and try the 155s on your bike.


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## svinyard (Aug 14, 2017)

TimTucker said:


> If his next bike comes with 155s, just keep him on the 127s and try the 155s on your bike.


I think BB is a SRAM Dub one on the new bikes I'm looking at. Maybe I can yank the one out of our Yama Jama? I don't have all the details if it'll work. Unsure of the shell size on the Yama Jama.


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## Steve-XtC (Feb 7, 2016)

svinyard said:


> I have a 34"/86.3cm inseam and am also on 175. I rode 170's the other day on that Ripmo and it was fine. Maybe 165 would be too?
> 
> Regardless, at this point I might be able to take my 7yro 127mm cranks on his 20" Yama Jama and just put them on the kids next 24" bike and be good to go.
> 
> OR if the next bike comes with SRAM 155mm...I just cut them down to 130mm? I've never done that but there is a good machine shop here in town. I'd like to not have to drop a bunch of cash on new cranks/BB for a new bike.


Don't forget the pedal hole is 13mm (5/16ths) so you need to factor that in to minimum lengths and still have some material at the end.


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## svinyard (Aug 14, 2017)

Steve-XtC said:


> Don't forget the pedal hole is 13mm (5/16ths) so you need to factor that in to minimum lengths and still have some material at the end.


So if I wanted to chop some 155's down to 135...would that work? I'm guessing that may not be enough material and I'd have to drop down to 130mm.

Have you done this before? Is it challenging? I'm concerned about getting the hole drilled out right/straight/centered/etc and then having to purchase pedal taps too. Wondering if its worth it vs spending some money on cranks like TC or something.


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## Steve-XtC (Feb 7, 2016)

svinyard said:


> So if I wanted to chop some 155's down to 135...would that work? I'm guessing that may not be enough material and I'd have to drop down to 130mm.
> 
> Have you done this before? Is it challenging? I'm concerned about getting the hole drilled out right/straight/centered/etc and then having to purchase pedal taps too. Wondering if its worth it vs spending some money on cranks like TC or something.


Done it lots ... 25mm is a good guide. If you go much less then the end of the existing hole will be really close.

As to buy vs make ? I certainly got value from the pedal taps and 13mm drill bit. Note 13mm is slightly under the recommended hole for 5/16ths tap but then that's in steel. I prefer leaving a few thou extra for the thread.

The tapping part is simple but I tend to add grease and do 3forwards - 2 back to clear the swarf...

The drilling is scary first time...

first time I made a jig but it's actually not so hard to get straight. Dot punch then I pilot something like 5, 10 then 13. I use oak behind the crank to drill into or it can really torque up ... like broken wrist torque if it doesn't break through clean.

Decent bits go though like its cheese so the important bit is control the speed or you'll practically melt it with a fast drill .. just keep it so you get a good clean swarf not breaking off.

An old pedal is useful in the existing hole as a guide but I just use my hand rechargeable.










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## jochribs (Nov 12, 2009)

Steve and Svinyard, to avoid the torque from grab, use some sort of cutting fluid while your drilling through. Something viscous will work fine, like 3 in 1 or even motor oil. WD-40 will work in a pinch. 

Funny story about drill torque. I had a co-worker that had long hair and it got wrapped up in the drill as he was drilling through something. It wound up super fast and when it got tight to his head, the drill swung up and clocked him with the battery. Nearly knocked him off the ladder he was on. He then had to reverse it to unwind his hair.


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## rabitoblanco (Feb 21, 2017)

jochribs said:


> Steve and Svinyard, to avoid the torque from grab, use some sort of cutting fluid while your drilling through. Something viscous will work fine, like 3 in 1 or even motor oil. WD-40 will work in a pinch.
> 
> Funny story about drill torque. I had a co-worker that had long hair and it got wrapped up in the drill as he was drilling through something. It wound up super fast and when it got tight to his head, the drill swung up and clocked him with the battery. Nearly knocked him off the ladder he was on. He then had to reverse it to unwind his hair.


Oh man that sounds like an awful comedy!

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## rabitoblanco (Feb 21, 2017)

Thought you guys would get a kick out of this-- while I'm here trying to figure out the difference of millimeters for his 24" bike, I turned around yesterday to find Rowan riding my (adult, Small frame, 26") bike... 

__
http://instagr.am/p/BxD4QtgAIpW/

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## Cerpss (Sep 13, 2015)

Still at the point of crank paralysis for my 51" with I think 20" inseam 8.5 yr old daughter. Struggling with 140mm vs the 152 that are stock on her Liv Enchant 24. She has the seat slammed because that's where she's comfortable. She's already not getting full leg extension with this on the 152mm. Going 140 seems like even worse extension. Once I get that nailed down I can decide between the trailcraft 104bcd or DM cranks.


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## Eneen (Jul 4, 2017)

My daughter is 6, has 52cm inseam and uses 114mm cranks. 152mm and 140 are both too long for sure and will hurt her knees. IMO 127mm would most probably be optimal. 152mm uses my wife with about 76cm inseam.


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## Steve-XtC (Feb 7, 2016)

Cerpss said:


> Still at the point of crank paralysis for my 51" with I think 20" inseam 8.5 yr old daughter. Struggling with 140mm vs the 152 that are stock on her Liv Enchant 24. She has the seat slammed because that's where she's comfortable. She's already not getting full leg extension with this on the 152mm. Going 140 seems like even worse extension. Once I get that nailed down I can decide between the trailcraft 104bcd or DM cranks.


Too long cranks lead to a lower saddle so they can pedal 
lower saddle means the saddle is further forwards (due to seatpost angle)
saddle further forwards leads to stand over moving forwards which usually due to top tube angle means less standover but either way they are pushed forwards leading to loss of confidence... leading to slammed saddle.


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## Steve-XtC (Feb 7, 2016)

Eneen said:


> My daughter is 6, has 52cm inseam and uses 114mm cranks. 152mm and 140 are both too long for sure and will hurt her knees. IMO 127mm would most probably be optimal. 152mm uses my wife with about 76cm inseam.


My 9yr old rides an adult XS with 142mm cranks.
Couldn't guarantee his height but he says it's 143cm


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## rabitoblanco (Feb 21, 2017)

Cerpss said:


> Still at the point of crank paralysis for my 51" with I think 20" inseam 8.5 yr old daughter. Struggling with 140mm vs the 152 that are stock on her Liv Enchant 24. She has the seat slammed because that's where she's comfortable. She's already not getting full leg extension with this on the 152mm. Going 140 seems like even worse extension. Once I get that nailed down I can decide between the trailcraft 104bcd or DM cranks.


My son is also 51" --We just installed 127 mm Spawn cranks on his 24" and the difference in how level his hips stay is enormous. 
(Much thanks to several of you here--Steve, Chris et al...)
Not a particularly good photo below, but this is with his seat at "street height" and gives you some idea of hip angle and leg extension. 
On the trails, we tend to ride with the lower seat, usually standing, and I'm waiting to see what that will look like. Will report back!









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## svinyard (Aug 14, 2017)

Ahhh yeah that what I was hoping to see. We have those cranks on our 20". I just need to swap for the shimano BB on the 24" and put those cranks on. His knee height/angle there looks ideal from the info I've seen on Dynamic Bicycles site etc. I ran most of the various Crank calculators the other day. Most had my 51" son riding around 125mm cranks. Some less, some more. I think the highest was 140mm tho that Calc was somewhat simplistic. It's kids so it's hard to tell but that Pic shows that it looks fairly decent to my less than expert eyes.

Fwiw I put my kid on 155mm cranks a couple months ago on a 24" bike and his knees came up really high. Like 90 degree angle. Apparently it's supposed to be closer to 70d.


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## Steve-XtC (Feb 7, 2016)

rabitoblanco said:


> My son is also 51" --We just installed 127 mm Spawn cranks on his 24" and the difference in how level his hips stay is enormous.


I think this is a bit of leap-of-faith. 
It's hard to imagine just how much crank length changes so many things. 
This is possibly doubly so since adult bikes have traditionally ignored crank length. 
I'd never thought of this for myself until I encountered it with Jnr.

Once you do the change the difference is (in my experience) usually more dramatic than expected


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## Desertride (Nov 1, 2012)

Does anyone know if it's possible to buy the Sunrace FCM80T 160mm 30t that I see speced on a few kids bikes?


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## MXIV424 (May 30, 2018)

I've been shopping for lightweight 165mm cranks for my oldest's next bike and...they're not cheap https://bythehive.com/products/trs-race-carbon-cranks-gen4

Maybe if I beg they'll make the xcx in a 160???


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## End_User (Mar 29, 2004)

Just got the Brood Bike Co (aka Spawn) Styx Crankset in 130mm. This comes with an integrated BB and SRAM direct mount ring compatible. 

Here are my weights (sans chainring):

Drive Side: 364g
Non-drive arm: 204g
BB, spacers, HW: 158g

Thats 726g plus maybe 40-150g for a ring depending on material. 

Seems heavier than what I was hoping for. I will weigh the stuff coming off my Orbea MX20 Team Disc next. I hope its a net savings or that will be a disappointment, but of course this still allows me to use a smaller ring than what is possible with the stock Orbea, so its still a benefit.


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## End_User (Mar 29, 2004)

Update. The Orbea Mx20 Team Disc stock crankset (with 34T ring) and BB came in at 792g. Thats lighter than the new brood styx setup I just put on by about 66g! 

Granted, I put a steel 28T ring on the new setup that weighs 132g itself, but all things considered Id call it a negligible weight savings for the Brood Styx crank. Disappointed for a $115 crank/BB (not including ring), and yet also amazed that the Orbea, as a $500 bike, did so well.


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## wallander (Jul 22, 2018)

One pretty cheap weight saving is to swap the heavy Brood BB with a Shimano XT at 82g.

See my nerdy spread cheat in OP here https://forums.mtbr.com/families-riding-kids/yama-jama-20-put-diet-1098353.html


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## rabitoblanco (Feb 21, 2017)

A status update on the Spawn 127mm crankset:
the attached chainring is 32t, and that's too high for a six year old to 1x with --on hilly trails.
And because it's 104bcd, it's hard to go smaller chainring. 
(Assuming run of the mill rear cogs, not Sram Eagle!) 

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## TimTucker (Nov 9, 2011)

rabitoblanco said:


> A status update on the Spawn 127mm crankset:
> the attached chainring is 32t, and that's too high for a six year old to 1x with --on hilly trails.
> And because it's 104bcd, it's hard to go smaller chainring.


You can do 30t with standard rings.

Not sure how well these work, but as far as I know these rings with integrated guards are the only option out there to go to 26t or 28t on 104bcd;
https://usamadeco.com/collections/sharktooth-pro-104-bcd-integrated-guard


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## Feldybikes (Feb 17, 2004)

Was going to second the 30T suggestion. Also excellent call on those integrated bash rings. Not having seen them in person (but having a 127mm spawn crank), I'd wager they'd fit. FWIW, I've used a usamade ring on my bike and it's worked just fine. Maybe not the most durable (seems to be wearing faster than other rings) but I would think it would take several kids to wear one out. The potential added benefit of a 30T (or the integrated bash I'd guess) is that it's slightly offset to the inside which improves chainline to the bottom of the cassette which is a big deal if your kid has a bike with short stays.

Eagle was mentioned. Interestingly, a 32x36 with a 20" wheel is actually a slightly smaller gear ratio at 17.8" than a 32x50 with 18.6". So, plenty small. If Sheldon Brown's ghost (RIP) joins in this argument and brings up "gain ratio" (i.e. taking into account crank length), I'd concede that is a good point. However, how slow is one expecting a 5-8 year old to be able to ride before they fall over?


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## svinyard (Aug 14, 2017)

FWIW we got Prevelo Heir 140mm cranks (86$ Shipped!!) and XT BB (19$) for my sons Clash 24". They are the same as Trailcraft etc. The chain ring is a 30t and with a 10-42 cassette, it's been excellent on the climbs and def using the 10t cog at times too. I want sure how it'd work but it really has been seemingly ideal. I wouldn't go down to a 28t with the smalls wheels and cranks.

Also the prevelo chain ring isnt offset 3mm to towards the bike. Since the kids bike is Boost, I think it's actually an improvement as the ring is about dead center to the cassette. I'm not expert tho, is that a good thing or do you want it closer to the 42t?

So far so good tho.


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## guaruska (Aug 3, 2017)

I'm saying this with the best intent; imho I think the parent should watch closely to why the kid doesn't get up the hill with ex 30t front and 11-36t rear (just an example). Dont confuse not being able to hold balance at such slow speed with needing lower gearing.
My 6 yo had 38t front with 11-42t gears, 125mm cranks on 20" wheel and barely ever used lower than 3rd gear, even on really really steep and long hills. I was about to change to 40t front when his technique improved to such a degree that he was able to hold balance on lowest gear and technical terrain. But those situations were rare.


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## slowride454 (Jan 11, 2014)

I got the Trailcraft 140mm cranks with 28T ring. I'll be pairing it with a 11-42 Deore 10 speed group on a 26" bike for my son. I should have time to build it up in the next week.


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## thecreeper23 (Jun 28, 2013)

slowride454 said:


> I got the Trailcraft 140mm cranks with 28T ring. I'll be pairing it with a 11-42 Deore 10 speed group on a 26" bike for my son. I should have time to build it up in the next week.


I put together basically the same drivetrain for my son's bike, except it's a 27.5 and the cranks are 152 length. He loves it.


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## rabitoblanco (Feb 21, 2017)

Edit for clarification, I have a 9 speed DH (Zee) derailleur on old school 7 speed wheels here. That's why not all the sprockets are accessible, so he's actually got a 5 speed! 
As it happens, I realized the error in my adjustment and now he's got the five easiest speeds with the 32 teeth front cog, and is doing great for all kinds of terrain. We don't do a lot of long uphills, but instead have punchy climbs and technical descents more often.



guaruska said:


> I'm saying this with the best intent; imho I think the parent should watch closely to why the kid doesn't get up the hill with ex 30t front and 11-36t rear (just an example). Dont confuse not being able to hold balance at such slow speed with needing lower gearing.
> My 6 yo had 38t front with 11-42t gears, 125mm cranks on 20" wheel and barely ever used lower than 3rd gear, even on really really steep and long hills. I was about to change to 40t front when his technique improved to such a degree that he was able to hold balance on lowest gear and technical terrain. But those situations were rare.


This is good advice regardless of my specific situation.
Thanks for the advice above regarding options-- those integrated ones I hadn't seen before!

My kid's problem is the biggest ring was actually not accessible, so my 6-year-old was on a 32T front, and 14-24 in the back on 24" wheels. His balance is somewhere between really good and great, but that's some hard gears to push on blue and black climbs.

Meanwhile, his frame just broke so more modern wheels are going to change the game.

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## Eneen (Jul 4, 2017)

https://www.vpace.de/produkt/max-kinderkurbel/


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## heet (Oct 25, 2015)

svinyard said:


> FWIW we got Prevelo Heir 140mm cranks (86$ Shipped!!) and XT BB (19$) for my sons Clash 24". They are the same as Trailcraft etc. The chain ring is a 30t and with a 10-42 cassette, it's been excellent on the climbs and def using the 10t cog at times too. I want sure how it'd work but it really has been seemingly ideal. I wouldn't go down to a 28t with the smalls wheels and cranks.
> 
> Also the prevelo chain ring isnt offset 3mm to towards the bike. Since the kids bike is Boost, I think it's actually an improvement as the ring is about dead center to the cassette. I'm not expert tho, is that a good thing or do you want it closer to the 42t?
> 
> So far so good tho.


How did you get ahold of those cranks? They aren't available on their website.


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## thecreeper23 (Jun 28, 2013)

heet said:


> How did you get ahold of those cranks? They aren't available on their website.


https://forums.mtbr.com/families-ri...t-mount-140mm-cranks-86$-shipped-1105847.html


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## xprmntl (Oct 4, 2006)

Moved my 7 yr old down to a 142 mm. I have a 155 mm NX crankset with 28T chainring and a matching 68 mm threaded cartridge bottom bracket. Used for maybe 10 miles of road riding This is a special OEM set off of an Early Rider. $100 shipped.


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## abeckstead (Feb 29, 2012)

I have a 135mm truvativ crank that fits a square drive BB. Works great on 20"&24" wheeled bikes. It's new and never installed. I also have a bash guard and two different pull front derailleurs to go with it all. $100 hit me up!


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## xprmntl (Oct 4, 2006)

Moved my 7 yr old down to a 142 mm. I have a 155 mm NX crankset with 28T chainring and a matching 68/73 mm threaded cartridge bottom bracket. Used for maybe 10 miles of road riding This is a special OEM set off of an Early Rider 24T. $100 shipped.

No longer available.


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## Desertride (Nov 1, 2012)

I finally got around to shortening an old crankset I have lying around for my kid's 20 inch.


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## Desertride (Nov 1, 2012)

I forgot to post this, if anyone is looking for a very inexpensive option and is OK with a 36T ring: https://www.aliexpress.com/item/4000493417383.html?


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## xprmntl (Oct 4, 2006)

Desertride said:


> I forgot to post this, if anyone is looking for a very inexpensive option and is OK with a 36T ring: https://www.aliexpress.com/item/4000493417383.html?


Good value, but even with a 42T - 50T rear cogs, the gear ratio is still pretty large for any steep terrain--A 36T/42 is a 0.85 gear ratio and a 36T/50T is a 0.72, both pretty big for a climbing anything moderately steep.

I consider a 28T/42T combo one of the best options for its weight savings and decent gear ratio, and can be used with medium cage derailleurs;Otherwise a 30T/46T or 32T/50T are okay options--all these combos keep the gear ratio close to ~0.65, which is a decent granny. I wouldn't put 46T+ cassette on a 20" bike for derailleur ground clearance issues, and this would not be great for 24" either.

Additionally, this Aliexpress Prowheel crankset has a 45mm chainline (see Prowheel | PRA-11C(110/92)), which I believe is designed for road bikes with 130mm rear drop-out spacing. https://www.sheldonbrown.com/chainline.html. This will be problematic for current MTB set-ups (135 - 142 mm drop-outs; not to mention Boost at 148 mm), likely to cause shifting and wear issues.

And finally, the chainrings aren't narrow-wide, so expect lots of dropped chains if taking it off-road.

Weight is ~650g (https://www.aliexpress.com/item/32642055305.html) without square taper bottom bracket which generally run ~300g (e.g. Shimano UN55)

Do yourself and your grom a fast favor and plunk down for a Pevelo ($119) or Trailcraft ($159) 140mm with a NW 28T.


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## Desertride (Nov 1, 2012)

I just put that out there as a budget option. For my own kid, see the previous post, I cut down an old triple I had lying around and fitted a N-W + bashring.

However, in terms of gear ratio, I don't think you need a .65 on 20" wheel. The bike is barely moving at that point.


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## xprmntl (Oct 4, 2006)

True enough that a 20" with a 28T/42T combo is pretty low, about 13.7 gear inches. A arguable target for a granny is ~16 gear inches (similar to the old standard from triple cranks of a 22T/36T on a 26er). For a 20" bike, this would be ~ 33T/42T.

For crank length on a 20", current thinking seems to be 110-130mm. 140 mm likely better suited to a 24" bike (something with a frame size ~12-14").


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## terrasmak (Jun 14, 2011)

Round 2 BMX cranks are available from 100mm to 160 and have a 4 bolt spider available. I just put a set on my daughters race bike and may order 140'd for her MTB


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## xprmntl (Oct 4, 2006)

terrasmak said:


> Round 2 BMX cranks are available from 100mm to 160 and have a 4 bolt spider available. I just put a set on my daughters race bike and may order 140'd for her MTB


Looks interesting and reasonably priced, but no info on the website on crank interface (square taper ISO?), nor crank bolt circle diameter, nor weights. 100lb weight limit on all cranks (even 150- 165 mm crank)!? All the machining intracacy left on surface is styley, but a pain to keep clean. https://round2bmx.com/shop?olsPage=products/round2-v2


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## terrasmak (Jun 14, 2011)

Keep clean, I run them on a BMX bike without issue. Yes they are square taper. I would contact him and make sure is the proper MTB bolt pattern offered.


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## xprmntl (Oct 4, 2006)

Standard BMX 4 bolt pattern is 104 BCD, so smallest chainring would be 32T. after square taper bottom bracket and chainring purchase, going with direct mount cranks from Prevelo or Trailcraft or Spawn would be lighter and similar price, plus compatible down to a 26T chainring.


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## TimTucker (Nov 9, 2011)

xprmntl said:


> Standard BMX 4 bolt pattern is 104 BCD, so smallest chainring would be 32T. after square taper bottom bracket and chainring purchase, going with direct mount cranks from Prevelo or Trailcraft or Spawn would be lighter and similar price, plus compatible down to a 26T chainring.


FYI, I haven't tried them myself, but these are an option to get 28T or 26T on 104 BCD cranks:
https://www.amazon.com/USA-Made-SharkTooth-INTEGRATED-drivetrains/dp/B01NAT2NWS

They get around the size constraint by integrating a guard with the chainring and have the threaded holes to screw into as part of the guard.


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## xprmntl (Oct 4, 2006)

TimTucker said:


> FYI, I haven't tried them myself, but these are an option to get 28T or 26T on 104 BCD cranks:
> https://www.amazon.com/USA-Made-SharkTooth-INTEGRATED-drivetrains/dp/B01NAT2NWS


That adds a lot of offset to the chainring, inboard, and description doesn't list how much. Looks like ~6 mm offset, which could wreak havoc on chainline and thus shifting / wear. The Amazon reviews speak to this in chain rubbing on tire and rubbing on bash guard in high gear (small rear cog). YMMV, as most reviews were positive.


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## StanfordRacer (Sep 29, 2008)

How wide are most 24" kids frames at the point where the crank comes closest to the chainstays? The reason I am asking is that the Trailcraft direct mount cranks have a 168mm Q-factor, which is REALLY wide for a little kid. The HUP Kids Crankset has a 145mm Q-factor. HUP really seems to understand kids bike ergonomics, the only question is if it will clear the chainstays on kids mountain bikes. Assuming 10mm thick crank arms, the outside of the chainstays need to be ~125mm or narrower at the point where the end of the cranks reach. My son's Norco Charger measures 120mm at that point. Are they all similarly narrow? If so, why does Trailcraft go with such a wide Q-factor?


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## Darth Lefty (Sep 29, 2014)

It's not about kids per se, it's about tire size. Q-factor = max tire width plus tire clearance plus chain stay plus crank clearance plus crank thickness. MTB = about seven inches. 145 = road bike.

They also are doing it with a really short spindle, which is kind of cheating, reflected in their very small chain line. The bike I'm cleaning up for my kid now has about 7"=175 q factor and a 127 spindle, it could be 155 with a 107 spindle. To do a stunt like that the chain line would come in a whole centimeter and I'd at least need to have the ring on the outer position to keep the chain line realistic


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## GSJ1973 (May 8, 2011)

StanfordRacer said:


> The HUP Kids Crankset has a 145mm Q-factor. HUP really seems to understand kids bike ergonomics, the only question is if it will clear the chainstays on kids mountain bikes. Assuming 10mm thick crank arms, the outside of the chainstays need to be ~125mm or narrower at the point where the end of the cranks reach.


-Narrow Q-factor
-2.1" or wider Tires
-Light Weight

Pick 2


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## StanfordRacer (Sep 29, 2008)

I'm trying to figure out what would be ideal, because I've got a potential source that might be able to make what I want.  However, it's not going to be easy or cheap, so I'd only do it if that was really the only way to get the right geometry.

Darth Lefty, totally agree that reducing the chainline with a narrower bottom bracket isn't the right way to reduce the Q-factor. I'm trying to stick with ~45mm chainline, which is what came stock on the Norco Charger 24. If I can do it while keeping the right chainline, I think a 145mm Q-factor will clear my son's Norco Charger. See attached image. Does that look right, or is there anything I'm missing?

Can anyone confirm these are typical measurements on a 24" bike, and not totally unique to the Norco Charger 24:
1) ~120mm between outside of chainstays where the cranks would contact
2) ~45mm chainline


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## xprmntl (Oct 4, 2006)

Prevelo claims their Heir cranks have a 140mm q-factor.


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## terrasmak (Jun 14, 2011)

I'm so happy to see Q factor mentioned, both on my kids bikes are horrible. Giant 20 inch and Haro 24 inch bikes. Their BMX bikes are really tight on the Q factor, the 6 year olds bike has the crank arms shaved to allow it to clear the chainstay.


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## Veneto (Nov 3, 2017)

Ordered the 140mm prevelo for my daughter. Haven't mounted them yet but here is the weight without BB.


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## drbelleville (Jun 11, 2008)

There is also the Hope "Kids Crankset No Spider"


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## jestep (Jul 23, 2004)

drbelleville said:


> There is also the Hope "Kids Crankset No Spider"
> View attachment 1337037


Are you sure that's a legitimate product, it's definitely not on the hope website or with mainstream vendors.


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## TimTucker (Nov 9, 2011)

jestep said:


> Are you sure that's a legitimate product, it's definitely not on the hope website or with mainstream vendors.


Did some looking and it looks like it is (was?) a real product, but only in stock from a handful of UK retailers for what worked out to be around $260 for crank arms only:
https://singletrackworld.com/forum/topic/do-nice-kids-cranks-exist/

Can't seem to find anyone with them in stock anymore, so they may not be in current production.

I recently went ahead and ordered myself a set of 140mm Trailcraft cranks to try out. Had debated on trying the Prevelo cranks, but decided against it for a few reasons:

Prevelo seems to be only selling a complete package now for $120 and I only needed the arms, so total cost was slightly cheaper for Trailcraft
Trailcraft is using a 48 spline vs. 10 spline interface for the Prevelo cranks -- from experience with BMX cranks, cranks with more splines tend to have a little stiffer engagement and be less likely loosen / wear over time.
Slight edge in weight on the Trailcraft cranks.


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## xprmntl (Oct 4, 2006)

*Hope Kids Crankset Sources*



drbelleville said:


> There is also the Hope "Kids Crankset No Spider"
> View attachment 1337037


Why is it that people can't seem to use a search engine? The Kid's Hope cranks are likely not manufactured anymore, but appear to be in stock in a few places in EU, like https://www.bike-components.de/en/Hope/Kids-No-Spider-Cranks-p74887/ (where the pic likely came from)
They come in 135 and 150 mm. 209 Euro without chainring ($55-$70) + shipping to U.S. They're available in all the Hope colors, so if you're into the "bling" factor, this is likely the only option

Also https://activesport.co/Hope-Kids-Crankset-No-Spider
https://r2-bike.com/HOPE-Crank-Kids-Crankset-68-73-mm
https://www.swinnertoncycles.co.uk/.../hope-chainset-kids-crankset-no-spider-p73979
https://www.singletrackbikes.co.uk/m7b0s586p74663/Hope_Kids_Crankset_No_Spider


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## TimTucker (Nov 9, 2011)

xprmntl said:


> Why is it that people can't seem to use a search engine? The Kid's Hope cranks are likely not manufactured anymore, but appear to be in stock in a few places in EU, like https://www.bike-components.de/en/Hope/Kids-No-Spider-Cranks-p74887/ (where the pic likely came from)
> They come in 135 and 150 mm. 209 Euro without chainring ($55-$70) + shipping to U.S. They're available in all the Hope colors, so if you're into the "bling" factor, this is likely the only option
> 
> Also https://activesport.co/Hope-Kids-Crankset-No-Spider
> ...


I went through a few EU sites (including Swinnerton) and after about 4-5 showing out of stock I stopped looking.

There are other options for bling factor -- Neutrino Components has a 138 / 155mm dual hole crank and you can choose your color for anodizing:
https://neutrinocomponents.com/inde...ntroller=product&id_lang=1#/length-138_155_mm

Haven't tried the cranks, but came across them when ordering a 64 BCD oval chainring for my son's bike.

Another option for colors would be BMX race cranks, although options that you can fit a narrowwide chainring on are a little more limited.


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## xprmntl (Oct 4, 2006)

Some other economical options:
Sunlite 152 mm, fixed 32T, square taper for $23 https://www.amazon.com/gp/offer-listing/B003MNLZJW/ref=dp_olp_new_mbc?ie=UTF8&condition=new
Suntour XC Triple, 152 mm, square taper: https://www.amazon.com/SR-Suntour-C...et&qid=1590763420&s=outdoor-recreation&sr=1-1
Jitsie 140 mm square taper for 40 pounds: https://www.jitsie.com/en/cranks/46884-jis-square-taper-cranks-per-pair.html
Jitsie 150 mm ISIS https://www.jitsie.com/en/cranks/52425-isis-cranks-per-pair.html
Sinz 5 bolt 110 mm BCD, square taper for $60 https://www.nashbar.com/sinz-expert-lite-alloy-crank-square-135mm-92-8064/p1151844
HUP 135-155 mm, 104 BCD, Square taper for $74 + $25 shipping: https://www.ebay.com/itm/HUP-Kids-C...s-104bcd-4-bolt-Narrow-Q-Factor-/292921682205
PMC Lasco 5 bolt 110 mm BCD square taper for $40 + $20 shipping : https://www.ebay.com/itm/PMC-Lasco-...10-BCD-5-Bolt-155mm-165mm-145mm-/132507586022
Trek Dialed, dual length (two pedal holes) in triple or 32T rings for $40: https://www.trekbikes.com/us/en_US/...-cranks/trek-dialed-24-kids-crankset/p/10059/
4 Bolt 104 mm BCD Bling from Bombshell at $229: https://www.danscomp.com/bombshell-ratchet-cranks-purple-150mm-451219a4ax4x/p1132351


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## TimTucker (Nov 9, 2011)

To categorize a little:

Rived / fixed chainrings:

Sunlite 152 mm, fixed 32T, square taper for $23 https://www.amazon.com/gp/offer-listing/B003MNLZJW/ref=dp_olp_new_mbc?ie=UTF8&condition=new
Trek Dialed, dual length (two pedal holes) in triple or 32T rings for $40 -- * listed as being threaded for 1/2" pedals: https://www.trekbikes.com/us/en_US/...-cranks/trek-dialed-24-kids-crankset/p/10059/

Cranks that use trials freewheels instead of a regular chainring:

Jitsie 140 mm square taper for 40 pounds: https://www.jitsie.com/en/cranks/46884-jis-square-taper-cranks-per-pair.html
Jitsie 150 mm ISIS https://www.jitsie.com/en/cranks/52425-isis-cranks-per-pair.html

110 BCD:

Sinz 5 bolt 110 mm BCD, square taper for $60 https://www.nashbar.com/sinz-expert-lite-alloy-crank-square-135mm-92-8064/p1151844
PMC Lasco 5 bolt 110 mm BCD square taper for $40 + $20 shipping : https://www.ebay.com/itm/PMC-Lasco-...10-BCD-5-Bolt-155mm-165mm-145mm-/132507586022

64 / 104 BCD:

Suntour XC Triple, 152 mm, square taper: https://www.amazon.com/SR-Suntour-C...et&qid=1590763420&s=outdoor-recreation&sr=1-1

104 BCD:

HUP 135-155 mm, 104 BCD, Square taper for $74 + $25 shipping: https://www.ebay.com/itm/HUP-Kids-C...s-104bcd-4-bolt-Narrow-Q-Factor-/292921682205
4 Bolt 104 mm BCD Bling from Bombshell at $229: https://www.danscomp.com/bombshell-ratchet-cranks-purple-150mm-451219a4ax4x/p1132351[/QUOTE]


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## TimTucker (Nov 9, 2011)

Started adding some of these into a Google Docs spreadsheet if anyone wants to start using that as a basis for putting together a more comprehensive list:

https://docs.google.com/spreadsheets/d/1VerkFozfeKnjMJB2vcj_1ZNPqTdV03991Qh0Fe2w1oQ/edit#gid=0


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## StanfordRacer (Sep 29, 2008)

*Samox direct mount cranks*

Long story, but I finally have a 140mm crankset with a 28 tooth narrow-wide chainring and a narrow Q-factor for my son's 24" Norco Charger.

I started out looking at the Trailcraft direct mount cranks, but the 168mm Q-factor was too wide. BMX and road riders long ago figured out that narrower is better for kids and I figure it probably also applies to mountain biking.

So earlier this year I reached out to Samox in Taiwan, who makes high quality forged cranksets, many of which get rebranded. I was pretty sure they were Trailcraft's manufacturer and later I realized Prevelo's too. Samox was about to start production on some new narrow q-factor cranksets for MY2021. I worked with them to spec a direct mount, 2-piece, forged alloy crankset with narrow-wide, forged chainring. Specs are 143mm Q-factor and a 44.5mm chainline, which is identical to the original chainline on my son's bike.

It took a few months (the axles on the first batch were 7mm longer than I specd), but my son now has a sweet crankset. The chainline is perfect and the Q-factor is so narrow that I had to sand the crankarms a little for clearance (though I could have avoided that with BB spacers).

I was planning to do a bigger order after I made sure that they worked, but then came COVID and the reality of dealing with a Taiwanese manufacturer, international wire transfers, and surprisingly expensive shipping. Also, I later realized that the Prevelo Heir crankset is very similar, though in the photos it doesn't appear to have a narrow-wide, forged chainring.








On the bike








Tight q-factor
















With the extra right side crank


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## jochribs (Nov 12, 2009)

StanfordRacer said:


> Long story, but I finally have a 140mm crankset with a 28 tooth narrow-wide chainring and a narrow Q-factor for my son's 24" Norco Charger.
> 
> I started out looking at the Trailcraft direct mount cranks, but the 168mm Q-factor was too wide. BMX and road riders long ago figured out that narrower is better for kids and I figure it probably also applies to mountain biking.
> 
> ...


This, my friend is awesome!


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## tigris99 (Aug 26, 2012)

Oh nice, got me thinking. I put spawn cranks on my sons Rockster. Wish I had know about those before I ordered. 

Sent from my SM-N975U using Tapatalk


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## ausdb (Jul 31, 2008)

StanfordRacer said:


> Long story, but I finally have a 140mm crankset with a 28 tooth narrow-wide chainring and a narrow Q-factor for my son's 24" Norco Charger.
> 
> I started out looking at the Trailcraft direct mount cranks, but the 168mm Q-factor was too wide. BMX and road riders long ago figured out that narrower is better for kids and I figure it probably also applies to mountain biking.
> 
> So earlier this year I reached out to Samox in Taiwan, who makes high quality forged cranksets, many of which get rebranded. I was pretty sure they were Trailcraft's manufacturer and later I realized Prevelo's too. Samox was about to start production on some new narrow q-factor cranksets for MY2021. I worked with them to spec a direct mount, 2-piece, forged alloy crankset with narrow-wide, forged chainring. Specs are 143mm Q-factor and a 44.5mm chainline, which is identical to the original chainline on my son's bike.


Wow they look great, good work.


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## 53sled (Mar 11, 2016)

The Suntour Zeron 152mm are still going strong, they come with a 1x NW and a BB.


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## jaybert (Sep 10, 2020)

Bumping up this thread to get some advice. I purchased a nukeproof Cub Scout race 24” but it’s going to be oversized for my son. I figured I could help it a bit by getting a shorter crank but don’t really know what I should be looking for. 

Samox TAF38J 2 Piece Crank 152mm, 32T, BCD 104

He son will probably be around 4ft when he starts riding so guessing want something like 130mm or less. Anyone know what my options are? Probably want a 28T chainstay (? Is that the right term) as well based on my reading.


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## jestep (Jul 23, 2004)

jaybert said:


> Bumping up this thread to get some advice. I purchased a nukeproof Cub Scout race 24" but it's going to be oversized for my son. I figured I could help it a bit by getting a shorter crank but don't really know what I should be looking for.
> 
> Samox TAF38J 2 Piece Crank 152mm, 32T, BCD 104
> 
> He son will probably be around 4ft when he starts riding so guessing want something like 130mm or less. Anyone know what my options are? Probably want a 28T chainstay (? Is that the right term) as well based on my reading.


152 isn't terrible, not perfect, but you aren't dealing with a 175 or anything so should still be usable.

Do you know what crank spindle this uses? It uses an external cup BB with a 68mm BSA shell on the frame but I can't tell if it's 24mm, GXP, or something else from the pictures or description.


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## jaybert (Sep 10, 2020)

jestep said:


> 152 isn't terrible, not perfect, but you aren't dealing with a 175 or anything so should still be usable.
> 
> Do you know what crank spindle this uses? It uses an external cup BB with a 68mm BSA shell on the frame but I can't tell if it's 24mm, GXP, or something else from the pictures or description.


Thanks for responding!

Nope, unfortunately not. I just ordered the bike and the only details I have are the ones listed on the website that I pasted on the crank.


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## xprmntl (Oct 4, 2006)

jestep said:


> 152 isn't terrible, not perfect, but you aren't dealing with a 175 or anything so should still be usable.
> 
> Do you know what crank spindle this uses? It uses an external cup BB with a 68mm BSA shell on the frame but I can't tell if it's 24mm, GXP, or something else from the pictures or description.


Most likely a 24mm spindle, like the 175 mm Samox of similar design reviewed,here https://www.sauserwind.com/products/samox-crankset-review/

With my 8yr old son, it made a big difference in his comfort and endurance going from 155 mm down to 140 mm. I'd recommend just pulling that crankset and saving or selling it and installing the Heir or Trailcraft options in a better size.


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## jaybert (Sep 10, 2020)

xprmntl said:


> Most likely a 24mm spindle, like the 175 mm Samox of similar design reviewed,here https://www.sauserwind.com/products/samox-crankset-review/
> 
> With my 8yr old son, it made a big difference in his comfort and endurance going from 155 mm down to 140 mm. I'd recommend just pulling that crankset and saving or selling it and installing the Heir or Trailcraft options in a better size.


thanks. What exactly should I be looking at to find something that is compatible? The 20" cub scout has a 127mm that I assume is compatible, but googling it I couldnt find it being sold anywhere, so maybe a nukeproof specific part that they havent setup to sell separately yet.


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## xprmntl (Oct 4, 2006)

To be compatible with your current bottom bracket, the new crankset will need to have the same spindle diameter, 24mm in this case. If it has another size spindle (like 30 mm), you will need a new 68 mm bottom bracket for that particular size. Trailcraft and Heir (Prevelo) come with their own bottom brackets, but I believe they are both using 24 mm spindles. For Prevelo, you will need to email them to order.


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## jaybert (Sep 10, 2020)

Thanks! Looks like trailcraft it out into 2021. I emailed prevelo for some more details. Are there other options you would recommend on eBay/alibaba/etc that would be significantly cheaper or is the $130-$170 for the trailcraft or prevelo about the standard price I should expect to pay?



xprmntl said:


> To be compatible with your current bottom bracket, the new crankset will need to have the same spindle diameter, 24mm in this case. If it has another size spindle (like 30 mm), you will need a new 68 mm bottom bracket for that particular size. Trailcraft and Heir (Prevelo) come with their own bottom brackets, but I believe they are both using 24 mm spindles. For Prevelo, you will need to email them to order.


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## kabayan (Oct 25, 2004)

SourceBMX has Lasco square taper 104BCD cranks in 140mm, 150mm and 160mm lengths for $40 + shipping. In stock now.
Treefort Bikes has Suntour XCT Jr square taper 104BCD cranksets in 152mm and 160mm for $31. Out of stock now.


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## jaybert (Sep 10, 2020)

kabayan said:


> SourceBMX has Lasco square taper 104BCD cranks in 140mm, 150mm and 160mm lengths for $40 + shipping. In stock now.
> Treefort Bikes has Suntour XCT Jr square taper 104BCD cranksets in 152mm and 160mm for $31. Out of stock now.


Thanks. if I were to go square taper, presumably i'd need a 68mm, square taper bottom bracket also right? Ideally I'd find something in the 127mm and 140mm range that I could swap out just the crank arms between the 2 since I'd like to start him at 127mm, but once that gets a bit large move up to 140mm (and back to stock 152mm if possible).

(not saying i'm going to, as it sounds like square taper has some downsides, but for my own understanding of how all this works).

WOuld I be able to get this: https://spawncycles.com/spawn-cycles-alloy-cranks-127 and something like https://www.nashbar.com/shimano-un3...MI5Prg5I-F7AIVEODICh1enAsAEAQYASABEgIXafD_BwE for the square taper 68mm bottom bracket, or is there more to consider in doing the swap?


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## xprmntl (Oct 4, 2006)

jaybert said:


> Thanks! Looks like trailcraft it out into 2021. I emailed prevelo for some more details. Are there other options you would recommend on eBay/alibaba/etc that would be significantly cheaper or is the $130-$170 for the trailcraft or prevelo about the standard price I should expect to pay?


Big ticket bike gets you big ticket cranks. You can offset cost by selling 152s, here. Square taper bottom bracket significantly heavier unless axle is titanium. Also, f you go with a 104 BCD crank, you can only run down to a 32T chainring. I would try go with a 30T, available with a direct mount like Heir or trailcraft, to pair with the 11-46T cassette on it, if you'll be dragging the tot on any steep stuff


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## jaybert (Sep 10, 2020)

xprmntl said:


> Big ticket bike gets you big ticket cranks. You can offset cost by selling 152s, here. Square taper bottom bracket significantly heavier unless axle is titanium. Also, f you go with a 104 BCD crank, you can only run down to a 32T chainring. I would try go with a 30T, available with a direct mount like Heir or trailcraft, to pair with the 11-46T cassette on it, if you'll be dragging the tot on any steep stuff


thanks! I knew I read somewhere that the square taper brackets were not recommended. And to make sure i'm understanding this properly, the reason you cant go with something smaller than the 32T with 104 BCD is because the the bolt hole locations wouldnt allow a chainring with less teeth since they have a smaller diameter.

The more expensive ones with direct mount don't use bolts/dont have BCD at all, so therefore you can have a larger range to go with since you arent restricted by the minimum diameter from the bolt holes.


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## jaybert (Sep 10, 2020)

xprmntl said:


> To be compatible with your current bottom bracket, the new crankset will need to have the same spindle diameter, 24mm in this case. If it has another size spindle (like 30 mm), you will need a new 68 mm bottom bracket for that particular size. Trailcraft and Heir (Prevelo) come with their own bottom brackets, but I believe they are both using 24 mm spindles. For Prevelo, you will need to email them to order.


fyi, i talked to Prevelo, and he let me know that they just got more in stock, and would be selling them differently. He said to expect to see the components available on their website in the next few days, and able to purchase a bunch of different configurations. He mentioned both a 120mm and 140mm option. Given trailcraft is OOS until 2021, this may be my best option. I wonder if I should get both the 120mm and 140mm option, starting with 120mm and the moving to 140mm, but maybe thats overkill. 120mm is pretty close to 10% of my son's height right now but will hopefully be < 10% very shortly so not sure if its worth it.


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## nebio (Jul 25, 2019)

jaybert said:


> Thanks. if I were to go square taper, presumably i'd need a 68mm, square taper bottom bracket also right? Ideally I'd find something in the 127mm and 140mm range that I could swap out just the crank arms between the 2 since I'd like to start him at 127mm, but once that gets a bit large move up to 140mm (and back to stock 152mm if possible).
> 
> (not saying i'm going to, as it sounds like square taper has some downsides, but for my own understanding of how all this works).
> 
> WOuld I be able to get this: https://spawncycles.com/spawn-cycles-alloy-cranks-127 and something like https://www.nashbar.com/shimano-un3...MI5Prg5I-F7AIVEODICh1enAsAEAQYASABEgIXafD_BwE for the square taper 68mm bottom bracket, or is there more to consider in doing the swap?


if going with the square taper crank as you've considered, what spindle length is needed?

Considering this option for NukeProof Cub Scout 24 if unable to get shorter cranks that are compatible with the external BB that comes on the bike (prevelo, trailcraft etc..)

Looks like the link you posted is 122.5mm spindle length.

Apologies if this is ignorant, is that 122.5mm length standard for this size bike is using square taper? Somewhere on trailcraft site they mentioned that 113mm is common with 68mm BB shell ...


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## Steve-XtC (Feb 7, 2016)

113 is usual for 68mm (you might be able to get a 110.5 in for narrower)
If you get a Shimano UN55 BB ($15) the weight won't be significantly higher.. I cut down a Zee and the BB+cranks were 12g lighter than a UN55 + SRAM S600 (everything on the scales) Obviously the Zee isn't the lightest but it's less difference than I'd expected. 

Sq taper isn't cool.. but the disadvantgaes don't really matter to kids (like stiffness, they won't be laying down 2000w sprints)

You can get 30T 104BCD but they have the bolt part built in rather than holes.


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## TimTucker (Nov 9, 2011)

kabayan said:


> SourceBMX has Lasco square taper 104BCD cranks in 140mm, 150mm and 160mm lengths for $40 + shipping. In stock now.
> Treefort Bikes has Suntour XCT Jr square taper 104BCD cranksets in 152mm and 160mm for $31. Out of stock now.


Small note on the Suntour cranks -- they're a triple, so they work with both 104 BCD and 64 BCD.

I have the 152mm with a 24T chainring on my around-town bike that I use to pull a bike trailer.


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## xprmntl (Oct 4, 2006)

jaybert said:


> fyi, i talked to Prevelo, and he let me know that they just got more in stock, and would be selling them differently. He said to expect to see the components available on their website in the next few days, and able to purchase a bunch of different configurations. He mentioned both a 120mm and 140mm option. Given trailcraft is OOS until 2021, this may be my best option. I wonder if I should get both the 120mm and 140mm option, starting with 120mm and the moving to 140mm, but maybe thats overkill. 120mm is pretty close to 10% of my son's height right now but will hopefully be < 10% very shortly so not sure if its worth it.


120 mm cranks will not be worth it if the child fits on a 24" bike. If you want something a little cheaper and heavier then I see Source BMX has Jet A 140mm square taper $40 for the crank arms + $20 for a 113 mm BB. https://us.sourcebmx.com/products/j...ce-cranks?variant=31946546479165&currency=usd
Amazon or Ebay has Chinese narrow-wide 30T chainrings for 104BCD, brands like Fomtor and Deckas for $15-$20.


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## jaybert (Sep 10, 2020)

Thanks for the input. All this info I was getting netted to it getting pricey to swap/complicated where i decided to just buy a Nukeproof Cub Scout race 20" bike (comes with 127mm cranks) for him to ride until he's ready for the 24", and the 20" will go to my daughter who is 2 years younger. At least a learned a bunch!



xprmntl said:


> 120 mm cranks will not be worth it if the child fits on a 24" bike. If you want something a little cheaper and heavier then I see Source BMX has Jet A 140mm square taper $40 for the crank arms + $20 for a 113 mm BB. https://us.sourcebmx.com/products/j...ce-cranks?variant=31946546479165&currency=usd
> Amazon or Ebay has Chinese narrow-wide 30T chainrings for 104BCD, brands like Fomtor and Deckas for $15-$20.


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## xprmntl (Oct 4, 2006)

Interesting that last year's Cub Scout ran 140 mm crank arms, stock https://www.chainreactioncycles.com/nukeproof-cub-scout-24-sport-kids-bike-2020/rp-prod186249

If go with Jet A square taper crankset or similar from Source BMX, it would be a direct swap to the stock bottom bracket, https://us.sourcebmx.com/products/j...ce-cranks?variant=31946546479165&currency=usd and then source a 30T, 104BCD narrow-wide chainring from Amazon or Ebay for $13-20--Fomtor or JGBike and others. Total cost under $70 with shipping if you have access to a crank puller and metric sockets to do yourself.


----------



## TimTucker (Nov 9, 2011)

xprmntl said:


> 120 mm cranks will not be worth it if the child fits on a 24" bike.


Honestly, most kids aren't going to notice anything but upsides to running 120mm cranks instead of 140mm, particularly due to the reduction in pedal strikes.

We'll be going with 120mm for 24" and maybe move up to something in the 127-135mm range at 26".

(I'm 5'10" and currently riding with 140mm cranks on my Stache)


----------



## rton20s (Aug 27, 2010)

Steve-XtC said:


> 113 is usual for 68mm (you might be able to get a 110.5 in for narrower)
> If you get a Shimano UN55 BB ($15) the weight won't be significantly higher.. I cut down a Zee and the BB+cranks were 12g lighter than a UN55 + SRAM S600 (everything on the scales) Obviously the Zee isn't the lightest but it's less difference than I'd expected.
> 
> Sq taper isn't cool.. but the disadvantgaes don't really matter to kids (like stiffness, they won't be laying down 2000w sprints)
> ...


^^^This^^^



xprmntl said:


> 120 mm cranks will not be worth it if the child fits on a 24" bike. If you want something a little cheaper and heavier then I see Source BMX has Jet A 140mm square taper $40 for the crank arms + $20 for a 113 mm BB. https://us.sourcebmx.com/products/j...ce-cranks?variant=31946546479165&currency=usd
> Amazon or Ebay has Chinese narrow-wide 30T chainrings for 104BCD, brands like Fomtor and Deckas for $15-$20.


^^^And this.^^^

Inexpensive square taper setups that are the proper length will be much better for your kiddo than a "better" bottom bracket/spindle design with crank arms that are too long. Direct drive is nice, if you really NEED 28T or smaller chain rings up front because they are doing a ton of climbing. Otherwise, the 30T options available for 104BCD should be just fine. Especially with the wide range cassette options we have available these days.


----------



## dcb (Sep 19, 2005)

*Suntour Zeron 152mm*

So I've recently been delving into this question as my daughter has recently graduated from a 24" Norco hardtail to an older full sus 26" bike. What I ended up with was a Suntour Zeron 152mm 1x30t crankset. It comes with a threaded bottom bracket as well. It's not light, about 867 grams according to my scale. I haven't installed them yet as I'm trying to figure out a wide range 9 speed cassette. Currently the bike has a 3 x SLX setup with 170mm cranks. As a bonus those cranks will go on my wife's bike which will be a better fit for her as well.

Total cost of the crankset and bb from Suntour was $71.96. I think one of the reasons the crankset is a little heavier is that it looks like they use the same crankarms and just drill the hole closer to the BB to adjust for length. Maybe that's common practice with manufacturers but I can't detect much absolute difference in crank length between the Suntours and the SLX's. If one really wanted to you could probably shave some of the end of the crankarms to save a little weight. I measure the distance from the outside hole in the Suntours to the end of the cranks at 17-18mm whereas it's about 7-8mm on the SLX's. I'd assume the Suntours are solid past the pedal hole so you could probably trim a cm off of both cranks. Again, to me that's not worth it unless she gets really into racing but to others maybe the weight loss would be worth it.

I'll post pics when I get it setup.


----------



## StanfordRacer (Sep 29, 2008)

That's really interesting regarding the Suntour Zeron. I've been eyeing that crank for my kid's next bike. I'd definitely take a grinder to the ends, both for avoiding rock strikes and weigh savings.

Regarding a wide range 9-speed cassette, the SunRace CSM990 11-40 is hard to beat for price and weight.


----------



## dcb (Sep 19, 2005)

Thanks! I hadn't seen that Sunrace cassette but it looks really interesting. I was thinking of going with Box components or Microshift but that Sunrace cassette would get me there for much less money. I've got to figure out if her derailleur will work with that cassette. It's an older XT long cage 9 speed. My experience with rear D's is that they can usually work with more teeth than what the manufacturer says they can. For example, I've used my Rival 1 with a 46 tooth rear cassette on my cross bike without issues. Her derailleur doesn't have a clutch though so maybe i'd want to get a new one for chain retention anyway.

have you used that cassette? I also noticed they've got a CSM980 that has a 42 tooth max cog but it says it's part of the juvenile series. I don't know what that means though and there's no info on their website that I could see that defines it. I've never used a Sunrace cassette before.

edit to add: Looking at the 980 cassettes the 11-40 version is 500 grams whereas the 990 version is 425 so maybe that's the difference.


----------



## TimTucker (Nov 9, 2011)

dcb said:


> Thanks! I hadn't seen that Sunrace cassette but it looks really interesting. I was thinking of going with Box components or Microshift but that Sunrace cassette would get me there for much less money. I've got to figure out if her derailleur will work with that cassette. It's an older XT long cage 9 speed. My experience with rear D's is that they can usually work with more teeth than what the manufacturer says they can. For example, I've used my Rival 1 with a 46 tooth rear cassette on my cross bike without issues. Her derailleur doesn't have a clutch though so maybe i'd want to get a new one for chain retention anyway.
> 
> have you used that cassette? I also noticed they've got a CSM980 that has a 42 tooth max cog but it says it's part of the juvenile series. I don't know what that means though and there's no info on their website that I could see that defines it. I've never used a Sunrace cassette before.


Have heard in a few places that some of the mid range Box cassettes are just rebranded Sunrace.

Have had the 10 speed 11-42 and 11-46 Sunrace cassettes on both my bike & my wife's bike. No issues there, they seem to have worked well.

I used the same 9 speed XT derailleur on my son's bike with an old 11-34T cassette and a narrow-wide chainring. No drops with mostly XC riding.


----------



## rton20s (Aug 27, 2010)

I've been using the wide range Sunrace CSM680 8 speed cassette on my rigid 29er since it was first released with no issues to speak of. I use it in combination with 30T NW chainring, SRAM X5 rear derailleur, KMC X9 chain and a Wolftooth RoadLink to provide the additional clearance I needed. 

I'm currently looking to add a wide range 1x drivetrain to my son's 24" bike. The original plan was to go Microshift Advent. Now I'm leaning toward a Microshift Acolyte setup once it is available, in order to save a few bucks. 

I think Microshift is really getting their stuff together with their latest wide range drivetrains. Not that Youtubers should be referenced as authorities above reproach, but both Hardtail Party and Biking Roots have given Microshift some pretty high praise recently. Biking Roots even did a shoot out comparing offerings from Sunrace, Microshift and Box.


----------



## StanfordRacer (Sep 29, 2008)

dcb said:


> have you used that cassette?


I haven't used the CSM990 yet--that's for the next bike. But my son is using a 40 tooth SunRace 8 speed cassette right now with a 9-speed long-cage Alivio derailleur with zero problems.


----------



## dcb (Sep 19, 2005)

alrighty then. I'm going to grab one of the Sunrace cassettes. I'll take some pics of the whole thing when I get it setup. Thanks to all!


----------



## TimTucker (Nov 9, 2011)

For those who are curious, Prevelo now has their Heir cranks listed:
https://prevelo.com/collections/heir/products/heir-direct-mount-crank

ala carte pricing:
$79 for crank arms
$29 for SRAM direct mount chainring
$19 for Shimano 24mm bottom bracket


----------



## terrasmak (Jun 14, 2011)

Talking with Round2 , they are going to make some 4x104 spiders so the mtb crowd can run his cranks with the common 30ish narrow wide mtb chainring. I mentioned the spider needs to be double sided so we can decide what wil work best for chainline. Any input or suggestions , call Guy at Round 2.


----------



## gooey1 (Jun 5, 2017)

TimTucker said:


> For those who are curious, Prevelo now has their Heir cranks listed:
> HEIR Direct Mount Crank
> 
> ala carte pricing:
> ...


I bought the crank only and will be building a Kotori up with it in the weeks to come. The crank looks and feels
very good in the hand. Customer service was above and beyond in all respects. It was shipped to Japan in
less than a week from initial contact at a very reasonable shipping cost.


----------



## jaybert (Sep 10, 2020)

TimTucker said:


> For those who are curious, Prevelo now has their Heir cranks listed:
> HEIR Direct Mount Crank
> 
> ala carte pricing:
> ...


Any idea what the preload spindle bolt for the non drive side size is? I kind of stripped mine when tightening it (think I didn't have the bit in all the way and it slipped out). I asked prevelo and they said they don't have any spares for sale but maybe in 60 days. Not sure how standard or not standard these are and if I can just order some from elsewhere


----------



## nebio (Jul 25, 2019)

jaybert said:


> Any idea what the preload spindle bolt for the non drive side size is? I kind of stripped mine when tightening it (think I didn't have the bit in all the way and it slipped out). I asked prevelo and they said they don't have any spares for sale but maybe in 60 days. Not sure how standard or not standard these are and if I can just order some from elsewhere


The Prevelo Heir cranks I recently put on my kids bike are are made by Samox.
You might have luck if you out reach them.
I have emailed Samox through their website in the past and gotten a personal response within a couple days


----------



## gooey1 (Jun 5, 2017)

Accessories - Samox guessing it is the BL-11 or maybe BL-07


----------



## jaybert (Sep 10, 2020)

gooey1 said:


> Accessories - Samox guessing it is the BL-11 or maybe BL-07


def not either of those. it has a much wider head (and i think the actual bolt is much thicker...but now I don't remember and dont want to risk uninstalling it and checking).

It looks closer to BL-A06, but that listed for an e-bike. I actually ordered one of those in case its that one (was $5 shipped, so worth a shot).

The bolt head is ~24mm diameter. Hard to get an exact measurement since its installed but its going to be very close to there.

Edit: took a closer look at the BL-A06 specs on samox's page. I think this is too wide. M20 apparently = 30mm? at least for a hex bolt. M16 = 24mm, but maybe its different for a round bolt like this vs. a hex bolt, not sure

edit2: hm, looking at other spindle bolts, the M20 seems to actually represent the width of the bolt itself, which I cant measure on my current one unless I remove it. I emailed Samox, hopefully they'll have more information.


----------



## gooey1 (Jun 5, 2017)

jaybert said:


> def not either of those. it has a much wider head (and i think the actual bolt is much thicker...but now I don't remember and dont want to risk uninstalling it and checking).
> 
> It looks closer to BL-A06, but that listed for an e-bike. I actually ordered one of those in case its that one (was $5 shipped, so worth a shot).
> 
> The bolt head is ~24mm diameter. Hard to get an exact measurement since its installed but its going to be very close to there.


Sorry I was half asleep when I read that. The Heir bolt thread diameter is approximately 17mm. From cap center to base length is 19mm. with about 17mm of actual insert length, and 12 or 13mm of actual thread.


----------



## jaybert (Sep 10, 2020)

gooey1 said:


> Sorry I was half asleep when I read that, the Heir bolt thread diameter is approximately 17mm. From cap center to base length is 19mm. with about 17mm of actual insert length, and 12 or 13mm of actual thread.


Thanks for the measurements. Doesn't seem like any of the bolts on Samox's website match unfortunately. I do have it installed so unless Samox can help me out, I'll just wait for prevelo to get them back in stock and order a couple. I have it installed fine so I'll just be careful and hopefully not need to remove it until I have a replacement.


----------



## gooey1 (Jun 5, 2017)

jaybert said:


> Thanks for the measurements. Doesn't seem like any of the bolts on Samox's website match unfortunately. I do have it installed so unless Samox can help me out, I'll just wait for prevelo to get them back in stock and order a couple. I have it installed fine so I'll just be careful and hopefully not need to remove it until I have a replacement.


No problem, good luck with it!


----------



## Sendit-dad (Mar 17, 2021)

rton20s said:


> ^^^This^^^
> 
> ^^^And this.^^^
> 
> Inexpensive square taper setups that are the proper length will be much better for your kiddo than a "better" bottom bracket/spindle design with crank arms that are too long. Direct drive is nice, if you really NEED 28T or smaller chain rings up front because they are doing a ton of climbing. Otherwise, the 30T options available for 104BCD should be just fine. Especially with the wide range cassette options we have available these days.


You CAN get a 28t 104BCD chainring. I've bought two of these and they work great. Amazon.com : USA Made 104mm BCD SharkTooth Pro Integrated Mountain Chainring and Guard fits 1/9/10/11-Speed drivetrains (28 Tooth) : Sports & Outdoors


----------



## JackOfDiamonds (Apr 17, 2020)

The 28t 104BCD chainring is sick! I'm going to try one on bigger bikes. To be honest, I find a 30T does fine on 20" bike because of the small wheel. A 30/28 is about 21 gear-inches on a 20-inch bike, which is pretty low.

If you've seen my other threads you already know I go to extreme lengths to build ultralight kids bikes so for my smaller kids, I normally go full-handcraft and make custom cranks. My usual crankset and BB together weight about 250g, which is less than a Shimano BB by itself, not to mention the heavier BB shell. Once the bikes get a little bigger, I'm willing to use a 68mm BB, I use Answer Mini cranks or LDC BMX cranks. These are available in 5mm increments from 105mm up, but both of those options are a little expensive and come with limited chainring possibilities. I get 104BCD spiders laser-cut for a few bucks so I can put 104BCD chainrings on Answer cranks.

The latest thing I've done is buy folding bike cranks off of Aliexpress. They are about $15 and come in like 105mm, 110, 115, 127mm and probably some other lengths. They seem to be ok quality but they always come with a steel sprocket staked on. Last weekend I came up with a way to chuck them in the lathe so I can put a 104BCD, Answer-pattern spider on them. Score! Short cranks and narrow-wide chainrings for about $20 each!

I'm also using Muqzi titanium BB's from Aliexpress. They come in sizes from 103mm up, and only cost about $30. HUGE weight savings vs. a steel BB.


----------



## ghj018 (Aug 13, 2005)

I'm curious about those arms you made, Pinch-bolt over square taper? Did you machine tapered holes or does the pinch clamp allow a straight hole to conform to the spindle taper?
Got me thinking about making some of my own.


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## JackOfDiamonds (Apr 17, 2020)

They are straight pinch bolt. The idea is copied from the Primo powerbite BMX cranks.


----------



## backinmysaddle (Jul 27, 2011)

I have the Suntour Zeron 152 crankset that I bought for an extra bike for my kids. Now that I built it up, I find that the chainring they sent (I did not specify Boost or no boost) has the chainline off, even from what they specify but nowhere near what it should be and gear 1 and 2 drop when I back pedal. The chainring looks really flat for a non boost, I mean my SRAM rings that are non boost have a much larger offset from the crank arm. Anyone else have this problem, and is it worth just ordering a nonboost ring and seeing if that works? Thanks!


----------



## rton20s (Aug 27, 2010)

backinmysaddle said:


> I have the Suntour Zeron 152 crankset that I bought for an extra bike for my kids. Now that I built it up, I find that the chainring they sent (I did not specify Boost or no boost) has the chainline off, even from what they specify but nowhere near what it should be and gear 1 and 2 drop when I back pedal. The chainring looks really flat for a non boost, I mean my SRAM rings that are non boost have a much larger offset from the crank arm. Anyone else have this problem, and is it worth just ordering a nonboost ring and seeing if that works? Thanks!


If the alignment looks off and you're dropping the chain in 1 & 2, it is probably worth spending the $34 for a new chainring and chainring tool.


----------



## hoffsta (Aug 17, 2010)

Pretty slim pickings on what's available these days. I'm trying to set up a 1x11 on an old early 90's RockHopper frame (73mm BB shell) for my kid and need 150-155mm cranks. From what I understand, I want about 48-49mm chainline and as narrow a Q as possible. I think that leaves me with square taper as my best choice since so much other stuff is out of stock or far more expensive than the entire bike.

I'm looking at something like the

Sinz Expert





Amazon.com : SINZ Expert Lite Alloy Square Taper Crank Arms : Sports & Outdoors


Amazon.com : SINZ Expert Lite Alloy Square Taper Crank Arms : Sports & Outdoors



smile.amazon.com





or Jet








Jet BMX Square Taper Race Cranks


High Quality, affordable BMX race cranks suited to the younger rider who rides a Mini, Junior or Expert sized Race Bike and made to fit any standard Square Taper (JIS) BB. Constructed from a tough 6061 forged aluminium for great stiffness and power transfer with a 4-bolt (104BCD) pattern built...




us.sourcebmx.com





BMX cranks. Neither list geometric detail. Has anyone tried these cheap BMX cranks on a 1x? Possible to get decent chainline using a longer spindle without throwing the Q all outta whack?


----------



## rton20s (Aug 27, 2010)

hoffsta said:


> Pretty slim pickings on what's available these days. I'm trying to set up a 1x11 on an old early 90's RockHopper frame (73mm BB shell) for my kid and need 150-155mm cranks. From what I understand, I want about 48-49mm chainline and as narrow a Q as possible. I think that leaves me with square taper as my best choice since so much other stuff is out of stock or far more expensive than the entire bike.
> 
> I'm looking at something like the
> 
> ...


Between those two, I would definitely go with the Jet. You'll have way more options for chainrings with the 4x104 BCD than the 5x110 BCD.

As you described Q factor can be affected by both the spindle length and the actual geometry of the cranks. What you have to be careful of as you get narrower and narrower is clearance around the chainstays. Some of the better BMX brands have a focus on narrow Q factors (LDC, Rennen,Von Sothen, Bombshell), but I'm not sure how well some may stand up to heavier riders and the abuses seen on a mountain bike.

If I were in your position, I would choose the crank arms first. Then go with the narrowest bottom bracket you think will work. Check for clearance at the chainstays, and if you need more width go to a longer spindle. For the chainline, you may luck out and get great alignment off the bat. If not, use bolt spacers as necessary to get the chainline dialed.


----------



## POAH (Apr 29, 2009)

Recently bought a 127mm DM crank from Alibaba. The company also supply 114mm cranks as well with DM. 






Lightweight Hollowtech Cnc Kids Children Direct Mount Crank Arm 114/127/152/170mm Bicycle Parts Chainrings Mtb Crankset - Buy Direct Mount Crank,Children Crankset,Mtb Crankset Product on Alibaba.com


Lightweight Hollowtech Cnc Kids Children Direct Mount Crank Arm 114/127/152/170mm Bicycle Parts Chainrings Mtb Crankset - Buy Direct Mount Crank,Children Crankset,Mtb Crankset Product on Alibaba.com



www.alibaba.com


----------



## TimTucker (Nov 9, 2011)

POAH said:


> Recently bought a 127mm DM crank from Alibaba. The company also supply 114mm cranks as well with DM.


Just ordered or did you have a chance to try them out yet?


----------



## POAH (Apr 29, 2009)

TimTucker said:


> Just ordered or did you have a chance to try them out yet?


on the bike the now


----------



## Eneen (Jul 4, 2017)

Wow they are really nice, what is qfactor?


----------



## POAH (Apr 29, 2009)

Eneen said:


> Wow they are really nice, what is qfactor?


**** knows.


----------



## Eneen (Jul 4, 2017)

Could you measure it? best is to measure seat tube diameter and distance from seat tube to outer crank face. If possible also crank thickness.


----------



## xprmntl (Oct 4, 2006)

What is your kid's maximum gate stance width?
Q factor of on a little kids bike?! C'mon.
The Chinese are probably making them at 190+mm Q just to mess with American kids.


----------



## xprmntl (Oct 4, 2006)

POAH said:


> on the bike the now


The link says minimum order 20 sets. Was this a group buy, or?


----------



## svinyard (Aug 14, 2017)

How do you order just 1? I’ve never done that before. Is it’s just like 20 or 30$?



POAH said:


> Recently bought a 127mm DM crank from Alibaba. The company also supply 114mm cranks as well with DM.
> 
> 
> 
> ...


----------



## POAH (Apr 29, 2009)

xprmntl said:


> The link says minimum order 20 sets. Was this a group buy, or?


bought two cranks. one 127 and a 152mm. You can buy a sample of one. All you do is message them with what you want. They send you an order filled out and you confirm and pay. 6mm offset ring for 135/142. 0 and 3mm give nasty chainlines.


----------



## xprmntl (Oct 4, 2006)

POAH said:


> bought two cranks. one 127 and a 152mm. You can buy a sample of one. All you do is message them with what you want. They send you an order filled out and you confirm and pay. 6mm offset ring for 135/142. 0 and 3mm give nasty chainlines.


Chainline and offset need will depend on bike's rear dropout/axle width in addition to the crank's offset dimensions and how bottom bracket set-up works on the bike of use. If the bike is Boost, 148 mm, usually 3 mm offset is right, non-Boost, 142 mm, then 6 mm.


----------



## POAH (Apr 29, 2009)

xprmntl said:


> Chainline and offset need will depend on bike's rear dropout/axle width in addition to the crank's offset dimensions and how bottom bracket set-up works on the bike of use. If the bike is Boost, 148 mm, usually 3 mm offset is right, non-Boost, 142 mm, then 6 mm.


small kids bikes are not likely to be boost and Sophie's isn't hence why 0 and 3 were nasty.


----------



## xprmntl (Oct 4, 2006)

POAH said:


> small kids bikes are not likely to be boost and Sophie's isn't hence why 0 and 3 were nasty.


Sometimes an XS adult frame, and 150 crank, can work for a 10+ yr old, which now generally come Boost. That's what my daughter is on. That's why I explained.


----------



## svinyard (Aug 14, 2017)

Hey did you check the weight on them by chance? I'm wondering how much they weigh without a chainring (loosely). I've got some pretty heavy SRAM 155mm cranks but if these are really affordable and light. I might have to grab a set.



POAH said:


> small kids bikes are not likely to be boost and Sophie's isn't hence why 0 and 3 were nasty.


----------



## stevelim (Jul 23, 2008)

svinyard said:


> Hey did you check the weight on them by chance? I'm wondering how much they weigh without a chainring (loosely). I've got some pretty heavy SRAM 155mm cranks but if these are really affordable and light. I might have to grab a set.


FYI I just picked up a pair of 152mm Samox cranks (SRAM DM) that weighed 526g (arms and spindle, no ring). They also have 155mm carbon cranks coming out soon.


----------



## POAH (Apr 29, 2009)

svinyard said:


> Hey did you check the weight on them by chance? I'm wondering how much they weigh without a chainring (loosely). I've got some pretty heavy SRAM 155mm cranks but if these are really affordable and light. I might have to grab a set.


I did but can't remember lol probably around 600-620g for BB and crank/28T ring


----------



## svinyard (Aug 14, 2017)

Where did you get those??



stevelim said:


> FYI I just picked up a pair of 152mm Samox cranks (SRAM DM) that weighed 526g (arms and spindle, no ring). They also have 155mm carbon cranks coming out soon.


----------



## POAH (Apr 29, 2009)

xprmntl said:


> What is your kid's maximum gate stance width?
> Q factor of on a little kids bike?! C'mon.
> The Chinese are probably making them at 190+mm Q just to mess with American kids.


145mm


----------



## TimTucker (Nov 9, 2011)

Thinking about this more, I wonder if they'd do fat bike cranks.


----------



## Eneen (Jul 4, 2017)

POAH said:


> 145mm


Wow, just wow! Could you also measure cranks thickness? Need to check if they can fit into my frame. Thx in advance.


----------



## POAH (Apr 29, 2009)

Eneen said:


> Wow, just wow! Could you also measure cranks thickness? Need to check if they can fit into my frame. Thx in advance.


_at the tips?_


----------



## Eneen (Jul 4, 2017)

POAH said:


> _at the tips?_


Yes, qfactor minus thickness x2 will give me frame clearance.


----------



## POAH (Apr 29, 2009)

Eneen said:


> Yes, qfactor minus thickness x2 will give me frame clearance.


15mm


----------



## zward (Mar 16, 2021)

POAH said:


> bought two cranks. one 127 and a 152mm. You can buy a sample of one. All you do is message them with what you want. They send you an order filled out and you confirm and pay. 6mm offset ring for 135/142. 0 and 3mm give nasty chainlines.


This sounds incredibly intriguing. I think 127mm 28T option would be about right for my daughter's Trek Wahoo 20 (new version of the Superfly). Stock is 140mm 28T and she is 46" tall with a 21" inseam. Any idea if a chain guard can be added? My kids have never had cranks without one and it makes me nervous for whatever reason.

I see a few Samox square taper options on Alibaba also, including a 127mm 28T (with chain guard!). This would be an easier swap and very cheap, but Q factor and chainline are unknown I guess. Looks like you can request a sample, but I'm not sure if that's really intended for individuals to purchase.





Bicycle Parts Alloy Forged Kids Bike Crankset - Buy Kids Bike Crankset,Alloy Bike Crankset,Alloy Forged Kids Bike Crankset Product on Alibaba.com


Bicycle Parts Alloy Forged Kids Bike Crankset - Buy Kids Bike Crankset,Alloy Bike Crankset,Alloy Forged Kids Bike Crankset Product on Alibaba.com



www.alibaba.com


----------



## thchen (Sep 24, 2013)

I went with a new Suntour XCT Jr 160mm and did the alumi chainring + bolts swap, and ended up at 782g, cost US$63 total:










versus an old spare Suntour riveted triple I pulled off a K2 24" with at 1064g (unpictured)

versus the original 175mm '95 LX on the XS stumpy which is only 669g









I wish I had the moola to go 1x hollowtech but DANG, 9spd shifters + chain + cassette == $$$ and I only paid < $200 for this all original Stumpy A1 (7 spd LX). Kid's just gonna have to suffer the extra 2 pound of weight on his bike I guess? To be continued.


----------



## thchen (Sep 24, 2013)

stevelim said:


> FYI I just picked up a pair of 152mm Samox cranks (SRAM DM) that weighed 526g (arms and spindle, no ring). They also have 155mm carbon cranks coming out soon.


I checked with Samox Taiwan on the Samox TAF38J 152mm used by Nukeproof/Norco, etc. and they replied:










So @stevelim must've picked up a set of take-offs?

Based on Samox's email, affordable 140/152 hollowtechs can only be had in the form for Suntour Zeron (not 104BCD), aliexpress, or the much pricier rebadged Samox from bike mfg's?


----------



## chiefsilverback (Dec 20, 2019)

thchen said:


> I checked with Samox Taiwan on the Samox TAF38J 152mm used by Nukeproof/Norco, etc. and they replied:


Trailcraft also appear to use the Samox cranks, if the part number on the back of the set installed on my son's new bike is anything to go by.


----------



## JackOfDiamonds (Apr 17, 2020)

I just bought some "Jet" BMX square taper cranks from Source BMX. They are 140mm which is what I wanted, and have a 4-bolt spider which is also what I wanted. But the question is, what the heck is going to be the chainline? I was planning to use them on a standard 135mm rear hub with 10spd cassette. What chainline does that actually require and how will that compare with a BMX crank? BMX bikes have 120mm hubs so I have no idea what to shoot for here.









Jet BMX Square Taper Race Cranks


High Quality, affordable BMX race cranks suited to the younger rider who rides a Mini, Junior or Expert sized Race Bike and made to fit any standard Square Taper (JIS) BB. Constructed from a tough 6061 forged aluminium for great stiffness and power transfer with a 4-bolt (104BCD) pattern built...




us.sourcebmx.com


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## Chris948 (Nov 23, 2010)

Just got some 114/28t cranks from Ali. Very impressed, about 2lbs lighter than stock! In a perfect world I would rather have 104s and my own ring, but not complaining for $15


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## JackOfDiamonds (Apr 17, 2020)

I have those exact cranks in my bin. I've modded some for a chainring spider before as shown further up the thread, you have to have a lathe but it's pretty easy if you do or know someone who does. I did some experiments making 3d-printed spiders a while back and it would probably be strong enough for a smaller kid.


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## rton20s (Aug 27, 2010)

JackOfDiamonds said:


> I just bought some "Jet" BMX square taper cranks from Source BMX. They are 140mm which is what I wanted, and have a 4-bolt spider which is also what I wanted. But the question is, what the heck is going to be the chainline? I was planning to use them on a standard 135mm rear hub with 10spd cassette. What chainline does that actually require and how will that compare with a BMX crank? BMX bikes have 120mm hubs so I have no idea what to shoot for here.
> 
> 
> 
> ...


You should be able to adjust for chainline pretty easily between placing the chainring inboard or outboard on the spider as well as spindle width selection.


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## rocwandrer (Oct 19, 2008)

Anybody tried these yet?



https://.aliexpress.us/item/3256804213106441.html


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## TimTucker (Nov 9, 2011)

rocwandrer said:


> Anybody tried these yet?
> 
> 
> 
> https://.aliexpress.us/item/3256804213106441.html


Wow, it looks like the 155mm version is only $35


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## JackOfDiamonds (Apr 17, 2020)

They have 89mm too. But how does the chainring mount?


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## rocwandrer (Oct 19, 2008)

JackOfDiamonds said:


> They have 89mm too. But how does the chainring mount?


It's compatible with SRAM direct mount rings.


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## jestep (Jul 23, 2004)

Looks like Hope added 155's for their evo crankset. Obviously not a budget friendly option but you could transfer the crankset indefinitely to new bikes as needed.


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## GVLaker09 (Mar 2, 2016)

Anyone have experience with the Suntour Zeron in 152mm? I should’ve asked before ordering but it was the only set I could find under $100 (and not on Aliexpress). Should be here next Monday, I’ll post an update when I get them.


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## DFWXC (6 mo ago)

GVLaker09 said:


> Anyone have experience with the Suntour Zeron in 152mm? I should’ve asked before ordering but it was the only set I could find under $100 (and not on Aliexpress). Should be here next Monday, I’ll post an update when I get them.



I ride the 165mm version, no issues at all but did think they were very heavy for the length. I am pretty sure mine were heavier than the stock 175 that came off my bike.

Likely indestructible for a kids bike


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## batboyv (Dec 10, 2021)

rocwandrer said:


> Anybody tried these yet?
> 
> 
> 
> https://.aliexpress.us/item/3256804213106441.html


I have a 140mm set on my daughter's bike and a 160mm set on my wife's Santa Cruz. The bottom bracket the cranks come with are junk. They use a standard 24mm Shimano BB and a GXP chainring. They seem fine for now and no issues to report.


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## rocwandrer (Oct 19, 2008)

batboyv said:


> I have a 140mm set on my daughter's bike and a 160mm set on my wife's Santa Cruz. The bottom bracket the cranks come with are junk. They use a standard 24mm Shimano BB and a GXP chainring. They seem fine for now and no issues to report.


That's exactly what I expected, thanks for the report!


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## chiefsilverback (Dec 20, 2019)

I need an extra set of ~152mm cranks and now I've got a 3 options on the table, a take-off pair of Samox from a Nukeproof Cub Scout that someone is selling, the Suntour Zerons and that Aliexpress Cruz set.

The Suntours appear to be the best value with a 10% discount for a first order, cranks + chainring for $72...


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## batboyv (Dec 10, 2021)

chiefsilverback said:


> I need an extra set of ~152mm cranks and now I've got a 3 options on the table, a take-off pair of Samox from a Nukeproof Cub Scout that someone is selling, the Suntour Zerons and that Aliexpress Cruz set.
> 
> The Suntours appear to be the best value with a 10% discount for a first order, cranks + chainring for $72...


I also have a set of 152 Suntour Zerons. They are no longer in use on my daughters bike for a couple of reasons. First, they are really heavy. Second, the chainring always dropped chains due to the teeth design. The only way to fix it was to buy their "wave" ring which is a proprietary mounting and requires a special tool to remove. Now the Zeron's sit in a storage bin. You are also stuck with the chainline since there is only one offset chainring offered in that mounting. With the GXP mounting, you can change the offsets to match your chainline. I'll sell you my Zerons.


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## batboyv (Dec 10, 2021)

batboyv said:


> I also have a set of 152 Suntour Zerons. They are no longer in use on my daughters bike for a 2 reasons. First, they are really heavy. Second, the chainring always dropped chains due to the teeth design (using an XT clutch RD). The only way to fix it was to buy their "wave" ring which is a proprietary mounting and requires a special tool to remove. Now the Zeron's sit in a storage bin. I'll sell you my Zerons.


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## batboyv (Dec 10, 2021)

I failed...tried to edit my last post and ended up replying to it.


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## GVLaker09 (Mar 2, 2016)

chiefsilverback said:


> I need an extra set of ~152mm cranks and now I've got a 3 options on the table, a take-off pair of Samox from a Nukeproof Cub Scout that someone is selling, the Suntour Zerons and that Aliexpress Cruz set.
> 
> The Suntours appear to be the best value with a 10% discount for a first order, cranks + chainring for $72...


I just put the Zerons on my daughters bike. People aren’t lying when they say they are heavy. I was shocked when I picked the box up off the porch. We’re going to use them for now, her bike is plenty light in every other area and I needed to start cutting some costs somewhere. I couldn’t justify a $200 crank set when there was one available for a third of the price. We’ll ride them for 2023 and maybe upgrade the year after if I think it will make a difference.
How much are the Samox cranks and what do they weigh?


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## batboyv (Dec 10, 2021)

GVLaker09 said:


> I just put the Zerons on my daughters bike. People aren’t lying when they say they are heavy. I was shocked when I picked the box up off the porch. We’re going to use them for now, her bike is plenty light in every other area and I needed to start cutting some costs somewhere. I couldn’t justify a $200 crank set when there was one available for a third of the price. We’ll ride them for 2023 and maybe upgrade the year after if I think it will make a difference.
> How much are the Samox cranks and what do they weigh?


The "Cruz" cranks from Aliexpress are fairly light and priced really well.


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## chiefsilverback (Dec 20, 2019)

GVLaker09 said:


> I couldn’t justify a $200 crank set when there was one available for a third of the price.
> How much are the Samox cranks and what do they weigh?


Trailcraft's crankset are re-badged direct mount Samox, and a 165mm set with a 30T ring weighs 615g according to my scales! I believe Prevelo use the same cranks branded as Heir but they only offer them in 130 and 140mm lengths. The 140mm Heirs are $160 with a chainring and BB vs $200 from Trailcraft.


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## GVLaker09 (Mar 2, 2016)

I thought that might be the case regarding Samox/Trailcraft/Prevelo when I was comparing pictures. We’re using 152mm so Heir wasn’t an option and Trailcraft was like $210 or more shipped. I saw options on Aliexpress but have never been confident using parts from there but that’s probably silly considering they likely all get made in the same place. If we decide we need to shed 200 grams next season I’ll probably go with an Aliexpress option. I wish Samox would sell direct because $200+ for a rebadged crankset is ridiculous. I got a great deal on a Timber 26 Carbon, lightweight Stan’s wheels, and we’re already quite a bit lighter than her 24” so I’m not too concerned about that bit of extra weight.


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## batboyv (Dec 10, 2021)

GVLaker09 said:


> I thought that might be the case regarding Samox/Trailcraft/Prevelo when I was comparing pictures. We’re using 152mm so Heir wasn’t an option and Trailcraft was like $210 or more shipped. I saw options on Aliexpress but have never been confident using parts from there but that’s probably silly considering they likely all get made in the same place. If we decide we need to shed 200 grams next season I’ll probably go with an Aliexpress option. I wish Samox would sell direct because $200+ for a rebadged crankset is ridiculous. I got a great deal on a Timber 26 Carbon, lightweight Stan’s wheels, and we’re already quite a bit lighter than her 24” so I’m not too concerned about that bit of extra weight.


Where did you find the deal on the lightweight stans wheels?


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## chiefsilverback (Dec 20, 2019)

Nukeproof use the Samox cranksets, but the 104BCD version so they are obviously a bit heavier. The part number stamped on the cranks are almost identical they all appear to be in Samox's '38J' series.


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## GVLaker09 (Mar 2, 2016)

batboyv said:


> Where did you find the deal on the lightweight stans wheels?


My daughter is on the school mountain bike team so the parents are always selling bikes and parts to each other before offering them up on Marketplace. Should be right around $2000 all in once I’m done with the build.


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## GSJ1973 (May 8, 2011)

chiefsilverback said:


> Trailcraft's crankset are re-badged direct mount Samox, and a 165mm set with a 30T ring weighs 615g according to my scales! I believe Prevelo use the same cranks branded as Heir but they only offer them in 130 and 140mm lengths. The 140mm Heirs are $160 with a chainring and BB vs $200 from Trailcraft.


FYI the Trailcraft cranksets uses an aluminum spindle (lighter) so this may or may not be important or worth the extra $40.00. But those counting all of the grams it is a place for additional weight savings. They are not the same ones Nuke Proof, Spawn, Prevelo, Commencal and others are using which have steel spindles. I think VPace is also using the same aluminum spindle Samox crankset Trailcraft uses.


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## Eneen (Jul 4, 2017)

This is some tech info of "Orca" crankset from alibaba that @POAH purchased. I wonder if it's possible to buy samples more than one time, I will probably need two 152mm sets.


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## rocwandrer (Oct 19, 2008)

Have Prevelo Heir now. Heartily endorse them for great product and great customer service.


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## jaybert (Sep 10, 2020)

trailcraft cranks / cranksets are currently on sale. I was about to order a set, but they only have 6mm offset chainrings, and I need 3mm for a boost rear. One option would be to order the crank from trailcraft (want 152mm which prevelo doesnt have) and the 3mm offset chainring from prevelo. I dont like playing double shipping though...becomes less of a deal when you only get the crank and not the set, and then need to pay shipping on the prevelo side also.


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## jaybert (Sep 10, 2020)

rocwandrer said:


> Have Prevelo Heir now. Heartily endorse them for great product and great customer service.


yea they're great. Ordered a replacement crank because of a stripped crank on 1 of the arms. Somehow UPS (or maybe it was fedex) said it was delivered but my security cameras/etc showed they never even came by when they said it was delivered. I let Prevelo know, and they sent one out the next day and dealt with the insurance claim on their end.


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## jaybert (Sep 10, 2020)

Just ordered 2 of them (152mm, 28t 3mm offset), was super simple. Shipping via UPS was almost as much as the 2 sets. Something like $55 for the 2 of them, and $45 shipping. Ended up being $110 after some alibaba transaction fee + tax. Said I should receive it in 10 days.

===



Eneen said:


> This is some tech info of "Orca" crankset from alibaba that @POAH purchased. I wonder if it's possible to buy samples more than one time, I will probably need two 152mm sets.
> View attachment 2009445


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## jaybert (Sep 10, 2020)

jaybert said:


> Just ordered 2 of them (152mm, 28t 3mm offset), was super simple. Shipping via UPS was almost as much as the 2 sets. Something like $55 for the 2 of them, and $45 shipping. Ended up being $110 after some alibaba transaction fee + tax. Said I should receive it in 10 days.
> 
> ===


Already got the dhl tracking # so they are pretty quick. Will weigh the 152mm + 28T when it comes in and can compare against the heir 140mm I have.

Edit: dhl says Monday delivery so a little over a week from ordering to when I should receive them


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## jaybert (Sep 10, 2020)

jaybert said:


> Already got the dhl tracking # so they are pretty quick. Will weigh the 152mm + 28T when it comes in and can compare against the heir 140mm I have.
> 
> Edit: dhl says Monday delivery so a little over a week from ordering to when I should receive them


Got them in…DHL always impresses. Took 2-3 days from when they started tracking in HK to get to my house. 

First pic is of the 140mm heir cranks. 530g. The 152mm orca + 28t chainring (came installed) weighs 560g. Given the orca ones are a bit longer + has a chainring I’d say it either weighs the same or less than the heir/samox ones

Also came with a bottom bracket. No clue of quality but attached a photo with the weight.

Mine came complete unbranded, maybe it’s just what they have in stock when it comes to small samples.


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## jaybert (Sep 10, 2020)

Eneen said:


> This is some tech info of "Orca" crankset from alibaba that @POAH purchased. I wonder if it's possible to buy samples more than one time, I will probably need two 152mm sets.
> View attachment 2009445



I mesured mine and got slightly different measurements. This is measured by itself, not mounted on a bike not sure if that will make a difference really. I got almost exactly 130mm inner distance, and a little less than 13.5mm width of each crank arm. So would put the q-factor right at 157. My measurer thing whose name I've now forgotten tops out at 155mm I think, so I just missed out on measuring the q-factor at once, but my individual measurements and it barely not reaching seem to be in line with each other.


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## Eneen (Jul 4, 2017)

jaybert said:


> I mesured mine and got slightly different measurements. This is measured by itself, not mounted on a bike not sure if that will make a difference really. I got almost exactly 130mm inner distance, and a little less than 13.5mm width of each crank arm. So would put the q-factor right at 157. My measurer thing whose name I've now forgotten tops out at 155mm I think, so I just missed out on measuring the q-factor at once, but my individual measurements and it barely not reaching seem to be in line with each other.


@jaybert
Thx a lot! This looks like awesome crankset indeed, weight is exceptional.
So looks like they are calculating Q including 0.5mm cutout in the crankarm: 127.7+13+13=153.7
This means, that this 130 is dimension requiring one spacer (127.7+2.3=130) and q-factor would be 130+13+13=156.
So, what's the chainline? If this 45.5 is without right spacer then chainline with 0mm offset chainring would be 45.5+2.3+3=50.8. Have you purchased -3mm or 0mm chainring? Could you try to measure chainline somehow, e.g. center of chainring to seat tube and add diameter/2 of seattube?
For me most important is to be able to fit this crankset into boost frame.


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## jaybert (Sep 10, 2020)

Eneen said:


> @jaybert
> Thx a lot! This looks like awesome crankset indeed, weight is exceptional.
> So looks like they are calculating Q including 0.5mm cutout in the crankarm: 127.7+13+13=153.7
> This means, that this 130 is dimension requiring one spacer (127.7+2.3=130) and q-factor would be 130+13+13=156.
> ...


I purchased it with the 3mm, and will be going on a reaper 26. Yea there is a small spacer that is included, 0.5mm sounds about right. Which side does that go on? Drive side between the ring and the BB? Or non-drive side between the BB and the crank arm? I will probably be installing it next weekend and can measure do more measurements then. Honestly I didnt even consider that it might not fit lol, thats about how much I know about bikes!

Edit: silly question I took a closer look at the spacer and it can only fit non drive side. 

Edit2: I couldn’t get my little measuring thing in there, but eyeballing it from the inner edge of the chain ring to the inner edge of the non drive side crank arm is 92mm. Could be off a bit because I aligned it on the inner edge of the chain ring and then eyeballed a parallel line from the tool down to the inner edge of the crank arm. I think it’ll be pretty close though. This is again uninstalled on the bike so not sure if that’s a useful measurement or not. 












Preload cap is plastic and includes a little plastic thing that slides in so you can tighten.


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## Eneen (Jul 4, 2017)

There're 3 spacers on the BB, they are 2.3mm. I guess there is only one (drive side only) required for 73mm and three (two for drive, one for non-drive) for 68mm, same as Shimano. From your measurements it looks like dimensions from drawing are just not right, provided without any 2.3mm spacers included. Anyway this will clear up when you install it.
I guess this 0.5mm spacer you are talking about allows proper tightening.
I was talking about 0.5mm cutouts here:


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## jaybert (Sep 10, 2020)

Eneen said:


> There're 3 spacers on the BB, they are 2.3mm. I guess there is only one (drive side only) required for 73mm and three (two for drive, one for non-drive) for 68mm, same as Shimano. From your measurements it looks like dimensions from drawing are just not right, provided without any 2.3mm spacers included. Anyway this will clear up when you install it.
> I guess this 0.5mm spacer you are talking about allows proper tightening.
> I was talking about 0.5mm cutouts here:


yea that spacer fits in the crank arm, it just fell off onto the spindle when i put them together and removed it. I have since put it back in the crank arm to keep it together. My measurements from earlier are with the spacer in place.

I'll get the measurements next week or whenever I get around to installing it on the bike.

Edit: oh oops you had cut the pic of where the pedal screws into the crank arm. No spacer there.


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## Eneen (Jul 4, 2017)

jaybert said:


> yea that spacer fits in the crank arm, it just fell off onto the spindle when i put them together and removed it. I have since put it back in the crank arm to keep it together. My measurements from earlier are with the spacer in place.
> 
> I'll get the measurements next week or whenever I get around to installing it on the bike.
> 
> Edit: oh oops you had cut the pic of where the pedal screws into the crank arm. No spacer there.


Sure, IHMO those cutouts make qfactor 156 instead of 157


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## jaybert (Sep 10, 2020)

welp, no one ever said it'd be easy...I got the crankset removal tool and got the raceface stock one off with minimal issues and went to dry fit the new crankset. The drive side seemed to be ok, but when I put on the non-drive side, the crank arm would hit the chain stay when it spun around...though now I think about it, that doesnt seem to make much sense? I would have thought it to be symmetric between the 2 sides, so I'm not sure how the drive side had room to spin freely, but the non-drive side didn't? Now i'm regretting putting the raceface ones back on so I can't really investigate anymore. It did not come with any spacers other than the ones that were included in the bottom bracket.

I'm open to any ideas, or if someone wants to buy 2x 152mm cranksets with 28T chainring (3mm offset) and 2 generic looking bottom brackets. It did not fit on the reaper, so maybe someone with a non-boost rear wheel will have better luck (probably should buy a new chainring meant for non-boost). I think I paid something like $110, will sell it for $100 shipped OBO within the USA. 



jaybert said:


> Got them in…DHL always impresses. Took 2-3 days from when they started tracking in HK to get to my house.
> 
> First pic is of the 140mm heir cranks. 530g. The 152mm orca + 28t chainring (came installed) weighs 560g. Given the orca ones are a bit longer + has a chainring I’d say it either weighs the same or less than the heir/samox ones
> 
> ...


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## jaybert (Sep 10, 2020)

jaybert said:


> welp, no one ever said it'd be easy...I got the crankset removal tool and got the raceface stock one off with minimal issues and went to dry fit the new crankset. The drive side seemed to be ok, but when I put on the non-drive side, the crank arm would hit the chain stay when it spun around...though now I think about it, that doesnt seem to make much sense? I would have thought it to be symmetric between the 2 sides, so I'm not sure how the drive side had room to spin freely, but the non-drive side didn't? Now i'm regretting putting the raceface ones back on so I can't really investigate anymore. It did not come with any spacers other than the ones that were included in the bottom bracket.
> 
> I'm open to any ideas, or if someone wants to buy 2x 152mm cranksets with 28T chainring (3mm offset) and 2 generic looking bottom brackets. It did not fit on the reaper, so maybe someone with a non-boost rear wheel will have better luck (probably should buy a new chainring meant for non-boost). I think I paid something like $110, will sell it for $100 shipped OBO within the USA.


Never mind it does rub on both sides. The non drive side was just more obvious because it had an additional cable holder that makes it stick out a little further. Both sides rub though, on the driver side it’s probably like 1mm (guessing you want more clearance than that…). Anyways def for sale if anyone is interested.


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## rocwandrer (Oct 19, 2008)

2mm spacer on the spindle spline?


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## jaybert (Sep 10, 2020)

rocwandrer said:


> 2mm spacer on the spindle spline?


I'm not sure, I can basically follow instructions when it comes to bikes...going off script and adding spacers/etc I am much less comfortable with. I would guess no though, would need to add spacers on both sides since both sides rub. It would need to be something like 2mm on the drive side, and then 2mm on the non-drive side, and then I'm not sure if that would be enough remaining for the non-drive side arm to tighten to and still be stable.


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## Eneen (Jul 4, 2017)

I'd put 1mm spacers on both sides... Your chainstays are pretty wide indeed.


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## jaybert (Sep 10, 2020)

Eneen said:


> I'd put 1mm spacers on both sides... Your chainstays are pretty wide indeed.


Thanks. As long as it clears I should be good? Do I need I worry about extra space for any sort of flexing/etc? 

How much spacers can I add before I need to start worrying about now having enough of the teeth on the spindle for the non drive side crank arm to attach to?


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## jaybert (Sep 10, 2020)

curiousity got the best of me so I removed the stock cranks for the 3rd time, so I could see what the Prevelo 140mm cranks looked like on it. I have an extra set with a stripped pedal thread on the non-drive side arm. The drive side had a ton of clearance, I calculated about 11mm. The non-drive side hits the chainstay, by like less than 1mm. I looked at the bottom bracket, and it is press fit, and no spacers on either side. Both sides of the BB are basically sitting flush against the frame so there doesnt appear to be any adjustments I can do there.


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## ladljon (Nov 30, 2011)

I have been running 125mm on road bike and 135mm on mtb and gravel bikes....I have adjustable long Ti square taper BB's just to get chainline right....loads of room.


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## JackOfDiamonds (Apr 17, 2020)

I would consider milling down the crankarms too, but I'm a hack like that...a hack with a vertical mill no less...


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## Eneen (Jul 4, 2017)

jaybert said:


> Thanks. As long as it clears I should be good? Do I need I worry about extra space for any sort of flexing/etc?
> 
> How much spacers can I add before I need to start worrying about now having enough of the teeth on the spindle for the non drive side crank arm to attach to?


2mm should be enough, 3mm is plenty. It flexes of course, you can check by standing havily on leveled crank left and right separately while locking rear brake. You can always tape on protection.

I guess you need spacers between crankarms and bb.


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## rocwandrer (Oct 19, 2008)

JackOfDiamonds said:


> I would consider milling down the crankarms too, but I'm a hack like that...a hack with a vertical mill no less...


Oh, yeah, if the clearance issue is only at the top of the crank arm, buzzing the end at a shallow angle in a belt sander or with a file and adding some small spacer(s) is the way on a kids bike for sure.


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## rocwandrer (Oct 19, 2008)

ladljon said:


> I have been running 125mm on road bike and 135mm on mtb and gravel bikes....I have adjustable long Ti square taper BB's just to get chainline right....loads of room.


Is there a present source for cup and long spindle BB parts these days? Back in the 90's I had a custom 100mm BB shell and a White Industries straight 17mm spindle with cartridge bearings pressed into aluminum cups, and that sort of thing would be perfect for my daughter's winter bike, but I can't find any.


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## Eneen (Jul 4, 2017)

rocwandrer said:


> Oh, yeah, if the clearance issue is only at the top of the crank arm, buzzing the end at a shallow angle in a belt sander or with a file and adding some small spacer(s) is the way on a kids bike for sure.


Yeah, Woom does this in-house


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## jaybert (Sep 10, 2020)

rocwandrer said:


> Oh, yeah, if the clearance issue is only at the top of the crank arm, buzzing the end at a shallow angle in a belt sander or with a file and adding some small spacer(s) is the way on a kids bike for sure.


For the prevelo one it is just the tip of the crank arm. Def less than 1mm, possibly something ridiculous as like .1mm. I can spin it and it will pass except it is ever so slightly rubbing on the edge when it passes by. But with flexing I assume I’d want to take off more. The somewhat complicating factor is I’d need to get a helicoil installed on this crank arm if I’m going to use this crankset and not sure if that will mean I can’t take out material or anything.


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## JackOfDiamonds (Apr 17, 2020)

A couple seconds on the belt sander would fix that right up.


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## jaybert (Sep 10, 2020)

JackOfDiamonds said:


> A couple seconds on the belt sander would fix that right up.


No belt sander but took a file to it. 



















So it clears now but I’m not sure how much more I can take off, especially given I would need a helicoil installed to make it usable again (or buy another set but I really don’t want to do that just to have to file it down again). I am guessing I need to take more off still so I don’t have clearance issues with flexing etc. 

Would you all suggest taking more off vs putting in like a 1 or 2mm of spacer between the bb and crank arm? Or maybe take a bit more off in combination with a 1mm spacer?


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## ladljon (Nov 30, 2011)

rocwandrer said:


> Is there a present source for cup and long spindle BB parts these days? Back in the 90's I had a custom 100mm BB shell and a White Industries straight 17mm spindle with cartridge bearings pressed into aluminum cups, and that sort of thing would be perfect for my daughter's winter bike, but I can't find any.


Yes White Industries has different lengths, but their turn around is slow....Phil Woods has several different lengths in steel...easy to find. I run 110-112mm for my Rohloff bikes.


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## JackOfDiamonds (Apr 17, 2020)

Looks good. You can take a lot more off of that before you have to worry about it.


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## rocwandrer (Oct 19, 2008)

jaybert said:


> No belt sander but took a file to it.
> 
> 
> 
> ...


When I was talking about spacers, I didn't realize the angle you were dealing with. You could easily take that back at that angle until you've cut into the back of the threaded hole and it would still likely be fine. Depending on the kid's weight and level of abusiveness, maybe much more.


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## Eneen (Jul 4, 2017)

jaybert said:


> No belt sander but took a file to it.
> 
> 
> 
> ...


IHMO you can sand off quite a lot as the hole is far from the tip. Take a look at woom picture I've posted above, they have whole tip rounded to get crankarm light.


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## jaybert (Sep 10, 2020)

jaybert said:


> I'm open to any ideas, or if someone wants to buy 2x 152mm cranksets with 28T chainring (3mm offset) and 2 generic looking bottom brackets. It did not fit on the reaper, so maybe someone with a non-boost rear wheel will have better luck (probably should buy a new chainring meant for non-boost). I think I paid something like $110, will sell it for $100 shipped OBO within the USA.


Figured I'd pop this. If anyone is interested in giving these 152mm cranksets a shot, I'll let them go cheap. It doesn't appear I'll ever get any use out of them. Make me an offer, or will trade for something interesting bike related that you have laying around.


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## Darth Lefty (Sep 29, 2014)

The DB Sync'r we just bought came with a SRAM SX crank at 155mm. Boost spacing, powerspline BB, steel ring.


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## Darth Lefty (Sep 29, 2014)

TimTucker said:


> Wow, it looks like the 155mm version is only $35





rocwandrer said:


> Anybody tried these yet?
> 
> 
> 
> https://.aliexpress.us/item/3256804213106441.html


I just clicked over there and ran into my lack of Chinese. Is there any reason the shorter 89-150 versions cost nearly 2x more than the longer 155-175 one?


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## rocwandrer (Oct 19, 2008)

Darth Lefty said:


> I just clicked over there and ran into my lack of Chinese. Is there any reason the shorter 89-150 versions cost nearly 2x more than the longer 155-175 one?


I translated the longer one as having a steel spindle. If the short one has a 7075 spindle, that could at least give you a benefit to justify the higher cost. I used Google lens to translate from a screen capture on Android. It was hokey. I had to manually select mandarin before it translated properly.


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## Darth Lefty (Sep 29, 2014)

Yeah given how bad the translation normally is I’m not surprised. You have to translate hobby and industry terms of art


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## s_ribs (17 d ago)

jaybert said:


> Figured I'd pop this. If anyone is interested in giving these 152mm cranksets a shot, I'll let them go cheap. It doesn't appear I'll ever get any use out of them. Make me an offer, or will trade for something interesting bike related that you have laying around.


Newbie on this forum so I can't PM just yet. I am interested, especially if you would be willing to sell one set which is all I need. Shoot me a PM please to talk details.


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## jaybert (Sep 10, 2020)

s_ribs said:


> Newbie on this forum so I can't PM just yet. I am interested, especially if you would be willing to sell one set which is all I need. Shoot me a PM please to talk details.


sent you a pm!


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