# Specialized 24" Hotrock FSR Build



## sharp21 (Jul 25, 2014)

Just picked this up for my son:









I may have slightly overpaid at $200, but it is a full suspension and I've been looking for one for a long time!

I've been through all the rebuild posts here and there are some great ideas. Another build I especially like is this one.

It is a little beat up; shifter housings are broken, tires are bald... but as it is getting the typical upgrade plus diet plan I'm not worried about any of that. I'll be real happy if I can keep the upgrades to within $500.

What I'd like to do:

Wheelset and drive train - I'd like to go to a 1x9 setup with thumb shifter. So that means rebuilt wheels with proper hubs. I'd heard good things about the Alex Ace20 rims and that's exactly what this bike already has installed!









The frame doesn't have disk break connections on the rear end so not sure if there is something I can add for that? Otherwise may look at hydraulic rim brakes.









New RD and shifter is a must.















And will probably need to change out the crank for a 5-hole









And of course am going to change out bars, stem, seat post, pedals, grips, etc. So that just leaves the suspension:















Not sure if there is a replacement available for the rear end. It'll probably be fine. The forks seem to be where the real weight savings and performance upgrade comes anyway. The build I linked to above just swapped in a 26" fork and called it a day. I've also read the threads about shortening the fork so that the rim brake still fits using a 24" wheel.

Not sure which way to go. I'm not made of $$$ so was thinking of using a Suntour XCR with disk brake and just go with that. I figure it would be more than enough for a little ripper. But then I'd really like to match it with disk brakes out back as that's the most important for the trails we ride...

Anyway, looking forward to the build. If you have suggestions for good value upgrades, wheel build recipes, or just general advise I am all ears.


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## Lemonaid (May 13, 2013)

I've never seen one of those. I think it could be a collectors item one day.


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## Lemonaid (May 13, 2013)

Personally I would try to keep everything stock. Change the brake pads and whatever else that needs to be cleaned up. Let your kid ride it for a couple of years and sell it in a couple years for more than what you paid for it. I'm not expert but it's a good looking bike and it might be worth keeping it the way it is in the long run.


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## sharp21 (Jul 25, 2014)

Lemonaid said:


> Personally I would try to keep everything stock. Change the brake pads and whatever else that needs to be cleaned up. Let your kid ride it for a couple of years and sell it in a couple years for more than what you paid for it. I'm not expert but it's a good looking bike and it might be worth keeping it the way it is in the long run.


The issue with that is that it is pretty heavy. I haven't weighed it yet but for a little guy, my boy will really benefit from putting the bike on a diet, with the main culprits being the wheels and fork.

I'm sure that I'll be able to move this bike along and recoup most of my investment when the time comes. It will likely go to my daughter next as she is two years younger. This bike will be in the family for a good 5 years so I want to make it as capable as possible.

It needs rubber anyway and the 7-speed out back needs to go if I'm going to install a proper shifter and RD, so the rear wheel is getting built no matter what. The fork is a boat anchor so it needs to go too, at which point that wheel will need to be built in order to fit a disk as the v-brake won't work.

The whole thing just snowballs from there...


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## MTB Pharm (Mar 10, 2007)

Drop the front derraileur and swap the rings to a single N/W ring
I’d keep the cranks, probably light enough and 4 bolt is probably easier to find rings. What length are they? Upgrade the bottom bracket to a sealed unit or ti unit. 

The handlebars on the kids bikes are usually steel, dunno what the FSR has. 
Swap the tires to some Rocket Rons should drop some weight.

Fork wise, an old SID is still the lightest option, but you have some good 24” air shock options now, but that may eat into your budget.


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## sharp21 (Jul 25, 2014)

I’ve been having trouble finding rocket Ron’s. 

Is there a shifter derailleur combo that will work for the freewheel 7speed hat is on the bike now? Looking at a full wheel build to change to a cassette but it’s really starting to add up. He’d be fine with the gearing as is but doesn’t like the grip shift. 

Everyone seems to go with an old Sid fork, but why not a new suntour air fork? If gong to 26” anyway why not go new?


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## blown240 (Nov 4, 2009)

Thats a cool little bike that I didn't even know existed! If it has 36 spoke wheels, you can get Deore hubs pretty cheap, then lace it with 24 spokes. That will take a bit of weight off. 

There is a company that makes a rear disc adapter, but for a kids bike, V brakes work pretty good. You could go disc front, V rear.


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## alexbn921 (Mar 31, 2009)

I'll add more later
24 Hotrock FSR 25lb

My son loves this bike and it fits it perfectly. The single best modification you can make is shorter crank arms! whent from 165mm to 145 bmx cranks with a shimano 34 road ring. Not NW, but no shift ramps and was cheap.

I used a zip tie on the rear linkage limit top out and to lower the BB after putting the shorter cranks on.

Alex rims are the best/lightest 24 rim brake rims. Shimano LX/TX rim brake hubs have the same flang diameter and spacing if you want to swap out the rear.

Running Rocket Ron tires with extra light tubes.

Stem is crazy heavy and I swapped to a 50mm with an old carbon bar.

post and seat are another great place to save cheap weight.

All 7-9 speed derailleurs will work with stock shifters. 
New cables/housing will dramatically change the effort to operate the shifter/brakes.

Sid fork is over 1lb lighter and actually works! Made an adapter for the brakes.

I would not put disks on this bike. Make it better and unless your kid is racing or crazy talented just have him ride the bike. He will be on a 26 bike in 2 years and will be ready for disks at that time.


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## MTB Pharm (Mar 10, 2007)

If you are looking for weight savings, then rocket rons will be your best choice. If you are looking for more aggressive knobs, then there is Brood Maxtion from Spawn

As for shifters, you'll can pick these up Shimano 7spd shifter I believe these should work.


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## MTB Pharm (Mar 10, 2007)

sharp21 said:


> Everyone seems to go with an old Sid fork, but why not a new suntour air fork? If gong to 26" anyway why not go new?


Like Alex mentioned above, The SID is a good pound lighter and used ones can be had for around $100. The Suntour is reasonable at about $160 or so. The advantage of the Sid also is it can be moved to a 26er if that is the kids next bike. Some of these 24 inch air forks weren't readily available either a few years ago.


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## sharp21 (Jul 25, 2014)

More great tips, thanks!

Still can't find Rocket Rons anywhere, or Moe Joe's. Only Kenda Smallblock V8's.

Also can't find a SID to modify! There are a few Manitou forks on ebay that I could shorten so I may go that route.

Interested in the V-brake adapter you made. What did you use for the mounting posts?

To start I'm going to switch it to 1x7 with a shorter cranks and BMX sprocket, new brakes, short levers, and a trigger shifter. New handlebars, stem and grips as well. And the new tires of course, when I find a good set.

Will do the fork as stage 2.


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## blown240 (Nov 4, 2009)

This may be a decent 24" tire.... 600 grams... Maxxis Snyper 24" DC Tire | Jenson USA


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## Shiftredline (Sep 4, 2012)

Also look at vee tire crown gem 24. Another awesome tire.


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## rabitoblanco (Feb 21, 2017)

@sharp21 So this is fun-- I posted on a different thread about the front fork, and see that we've both just bought this unusual bike within a week!

My Rowan is at the bottom of the height charts for this thing, so I'm looking exclusively at the 24" forks.

So far, have just put a shorter stem to start.









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## sharp21 (Jul 25, 2014)

rabitoblanco said:


> @sharp21 So this is fun-- I posted on a different thread about the front fork, and see that we've both just bought this unusual bike within a week!
> 
> My Rowan is at the bottom of the height charts for this thing, so I'm looking exclusively at the 24" forks.
> 
> ...


Congrats on the purchase!

I've already got a short stem (in red!) in the parts bin so that will be getting installed soon. As soon as payday hits next week I'm hitting the order button and getting the rest of he pieces to install.

Thanks all for the tire recommendations. I'd like something sub 500grams and don't mind paying for them.

I also like the idea of relaxing with fewer spokes but am also considering running tubeless.

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## MTB Pharm (Mar 10, 2007)

The Brood tire I posted is 560 grams but that is also for a 2.3 inch tread. $45 per tire is on par with the RRs. 

The Crown Gem looks interesting, and price is good $25 or $30, but no exact weight. Vee Tire lists weights for their of the tire sizes but does not show which size it matches to.


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## Shiftredline (Sep 4, 2012)

It’s 570g. It a big volume 2.25


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## sharp21 (Jul 25, 2014)

Shiftredline said:


> It's 570g. It a big volume 2.25


I think I read somewhere that there isn't clearance for much more than 2.1?

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## Shiftredline (Sep 4, 2012)

I have them on my sons trek mt220. I have no clearance issues. Not sure about the Hotrock FSR. The crown gems are also tubeless ready.


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## MTB Pharm (Mar 10, 2007)

That’s the Crown Gem right? If so, then for the price it really is pretty good. On the Vee tire website, it says wire bead... I found an eBay listing and the photo is of the tire folded. Is there a Kevlar beaded version?


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## ghabe (Mar 7, 2015)

MTB Pharm said:


> The Brood tire I posted is 560 grams but that is also for a 2.3 inch tread. $45 per tire is on par with the RRs.
> 
> The Crown Gem looks interesting, and price is good $25 or $30, but no exact weight. Vee Tire lists weights for their of the tire sizes but does not show which size it matches to.


I just bought the Brood tires in 20x2.2. They're not true to size. I measured them at 1.95in from outside knob to outside knob when mounted and inflated at 15psi. For reference, the 3 years old Bontrager XR1 Comp 20x1.85 they replaced still measured exactly 1.85in. So I would expect the 24in version to also be narrower than expected.

The claimed weight was accurate however. Exactly 445g as advertised for the 20in version.


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## Shiftredline (Sep 4, 2012)

They are the folding version


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## rabitoblanco (Feb 21, 2017)

Shiftredline said:


> They are the folding version


What does "folding" mean? I mean beyond that they fold, haha positives/negatives, etc please?


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## Shiftredline (Sep 4, 2012)

They are lighter then the wire beads and the crown gems are tubeless ready if you prefer to go that route.


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## rabitoblanco (Feb 21, 2017)

Shiftredline said:


> They are lighter then the wire beads and the crown gems are tubeless ready if you prefer to go that route.


Thank you! 
The Alex Ace 20s seem like some of the best options on wheels, but they're older-- what's everyone's thoughts on adapting regular wheels for kids to tubeless? 
From my readings, I've heard mixed results and generally not worthwhile it seems for adult tires.

-ridwan


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## alexbn921 (Mar 31, 2009)

Tubeless is great, but it also needs to be maintained. Is your kid riding in goat head thorns or bashing threw rock gardens? My guess is that tubes would be much easier to deal with at a kids riding level and aggression. Ghetto tubeless is your best bet. Split a tube down the top middle and lay it over the rim. Then mount the tire and trim off the excess tube.


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## sharp21 (Jul 25, 2014)

alexbn921 said:


> Tubeless is great, but it also needs to be maintained. Is your kid riding in goat head thorns or bashing threw rock gardens? My guess is that tubes would be much easier to deal with at a kids riding level and aggression. Ghetto tubeless is your best bet. Split a tube down the top middle and lay it over the rim. Then mount the tire and trim off the excess tube.


I'm going to get some Rocket Rons and some nice light tubes and call it a day. Any tube recommendations?


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## sharp21 (Jul 25, 2014)

In another coincidental turn of events, the neighbor kid just got a brand new Hotrock for his birthday.

Looks cool








Cheap forks








Only a 7spd. No shifter up front








I like this bash guard / chain tensioner combo!








This size is still a little big for the boys so I feel in a good position to lighten up my sons and make it fit a little better than the neighbors bike fits him. After watching the kids ride a bit and thinking about HOW they ride and the skill level I'm going to simplify the build slightly.

I found a set of SIDs for $100 locally. Was on the fence due to either needing a disk brake or a v-brake adaptor. Then I thought of my cruiser bmx and decided I'm going to do away with the front brake entirely, at least for now. The terrain we ride doesn't really need front brake but my son is typically grabbing that one. So he is going to go rear brake only for a while so he learns to use that properly.

So new rubber, new rear brake, single up the drivetrain and install new 7-spd trigger shifter. Shorter stem, lighter bars, seat and post.

I've got a lot of work coming up so don't have time to rebuild the wheels. I want to get him riding and comfortable on this bike ASAP.


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## jmossbarger (Oct 30, 2013)

Did you find the rocket rons? I ended up getting mine from Bikes Discount in Germany.

https://www.bike-discount.de/en/buy/schwalbe-rocket-ron-performance-addix-24x2.10-folding-662617

Looks like they have them. Shipping is reasonable, a week to 10 days if I remember correctly.

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## sharp21 (Jul 25, 2014)

One more question: Looking at replacement cranks - what BB do these bikes have? Wondering if a new BB is needed? Or just new square taper cranks...


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## sharp21 (Jul 25, 2014)

jmossbarger said:


> Did you find the rocket rons? I ended up getting mine from Bikes Discount in Germany.
> 
> https://www.bike-discount.de/en/buy/schwalbe-rocket-ron-performance-addix-24x2.10-folding-662617
> 
> ...


Found a few options:

https://blueskycycling.com/products/...SABEgKQO_D_BwE

https://www.dirtmerchantbikes.com/ki...s-for-24-bikes


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## MTB Pharm (Mar 10, 2007)

The BB is a standard 68mm. Width is about 113 if it recall. If yours is smooth, then I suppose you don't need to change it, otherwise a shimano sealed unit would be a good option if you are sticking with square taper. I bought a set of cranks from Flow for my daugther's bike; external bearing BB, standard 4 bolt chain rings

If you are on a budget, and you have some wrenching skills, you could try cutting down and re-tapping the pedal threads to shorten the existing cranks.


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## thesmokingman (Jan 17, 2009)

sharp21 said:


> In another coincidental turn of events, the neighbor kid just got a brand new Hotrock for his birthday.
> 
> Looks cool
> View attachment 1194099


Ack, look at the foot long head tube!


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## MTB Pharm (Mar 10, 2007)

sharp21 said:


> I like this bash guard / chain tensioner combo!
> View attachment 1194102


The chain tensioner is a steel plated piece. You're better off springing for a rear derailleur with a clutch or a light chain keeper. 
The bash guard is just thin plastic meant to keep the pant legs out of the ring.


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## thesmokingman (Jan 17, 2009)

I don't think that's his kids bike but a neighbors kids bike.


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## sharp21 (Jul 25, 2014)

thesmokingman said:


> Ack, look at the foot long head tube!


What does the long head tube imply, regarding handling or geometry?

Yeah the black one is the neighbors. We are keeping the RD out back

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## thesmokingman (Jan 17, 2009)

sharp21 said:


> What does the long head tube imply, regarding handling or geometry?
> 
> Yeah the black one is the neighbors. We are keeping the RD out back
> 
> Sent from my iPhone using Tapatalk


A head tube like that means a super high cockpit. It adds a ridiculous amount of height. Compare that to your kids bike. It's like riding a chopper.


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## alexbn921 (Mar 31, 2009)

uhhgggg. That other bike is complete crap. Everything about is wrong and I bet it weighs 30lb.
Isla and frog have kids bikes figured and it should be the goal mimic there design.

I used the stock BB square tapper and bmx cranks. Shorter cranks will make the BB feel higher and require a higher seat. This makes it hard to put your feet down. I unwound the rear spring to lower the BB and used a strong zip tie to prevent the suspension from extending all the way. You still get full travel with a lower bb and seat to ground measurement.

For tires and tubes I used
https://www.bike24.com/1.php?content=8;product=240863;menu=1000,2,103,202;mid[6]=1;pgc[3039]=3045

10 is the correct tube, but the 9 works and is lighter.
https://www.bike24.com/1.php?content=8;product=63753;menu=1000,2,103,203;mid[6]=1

https://www.bike24.com/1.php?content=8;product=5274;menu=1000,2,103,203;mid[6]=1


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## sharp21 (Jul 25, 2014)

alexbn921 said:


> uhhgggg. That other bike is complete crap. Everything about is wrong and I bet it weighs 30lb.
> Isla and frog have kids bikes figured and it should be the goal mimic there design.
> 
> I used the stock BB square tapper and bmx cranks. Shorter cranks will make the BB feel higher and require a higher seat. This makes it hard to put your feet down. I unwound the rear spring to lower the BB and used a strong zip tie to prevent the suspension from extending all the way. You still get full travel with a lower bb and seat to ground measurement.
> ...


Great, thanks!

I'm gonna change the cranks so I'll look at dialing out that rear suspension

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## GrayJay (May 16, 2011)

Suntour XCR is a pig at 2300+gr, it would likely outweigh the OEM RST fork that is on there now. Epicon is at least a bit lighter at 1700gr if you are stuck on buying an new suntour fork.

Good thread on kid-wheel rebuilding options;
http://forums.mtbr.com/families-rid...-wheel-build-40lb-rider-need-help-891768.html

How long is the stock crankset? It could work to replace the outer ring with a bash-guard and remove the inner chaingring for a 1X setup. Even if the crank is excessively long for him right now, it would likely work well in a couple of years to fit him on a XS 26" bike.


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## sharp21 (Jul 25, 2014)

I’ve found a Rockshox Sid already so am gonna go with that. 

I’ll measure the cranks later but don’t plan to reuse parts from this one on his next one. This will go to his sister when he is ready to step up. 


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## alexbn921 (Mar 31, 2009)

The stock cranks are 165mm and will be a good replacement for his next 26" bike. Even small mountain bike usually come with 175 cranks. I gave my cranks to a friend whos son is 11 and they fit him perfectly.


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## sharp21 (Jul 25, 2014)

Started ordering parts! Rocket Ron's on the way.

I wanted to double check front sprocket size before pulling the trigger. I'm going to reuse the stock cranks for now, need a NW sprocket up front.

What is the BCD and how many teeth would you recommend? I'm out at work otherwise I'd just measure it myself...


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## sharp21 (Jul 25, 2014)

One more question. I was going to order a 7-spd trigger shifter and a tektro brake lever for the rear. But I've got a Shimano 8-spd combination shifter / brake lever that is in great shape. Any reason I can't use that?

This is a pic of the front one, but you get the idea:


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## rabitoblanco (Feb 21, 2017)

I know the 8 speed will work, because that's what ours came with!

But this brake lever is very far out for Rowan's little hands. He's a good enough rider that he can make do, but something to keep in mind--in comparison to some of the individual brake levers that can be adjustable.









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## Steve-XtC (Feb 7, 2016)

> I'm going to get some Rocket Rons and some nice light tubes and call it a day. Any tube recommendations?


Kinda missed that... if your going RR I'd honestly go tubeless.... they are really light but pretty thin... it seems tempting fate to say this but we never had a puncture didn't seal on them but based on what I pulled out in terms of thorns and stuff we'd have gone through a near endless supply on tubes. (Your almost doubling the weight for no real benefit)

Obviously it's good to carry a spare tube anyway ....

If you're ripping tyres on sharp rocks then the RR's are not the best choice..


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## sharp21 (Jul 25, 2014)

That’s a great point. I’m trying to keep the budget in check but ultimately this is about building a confidence inspiring bike that fits great


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## sharp21 (Jul 25, 2014)

Steve-XtC said:


> Kinda missed that... if your going RR I'd honestly go tubeless.... they are really light but pretty thin... it seems tempting fate to say this but we never had a puncture didn't seal on them but based on what I pulled out in terms of thorns and stuff we'd have gone through a near endless supply on tubes. (Your almost doubling the weight for no real benefit)
> 
> Obviously it's good to carry a spare tube anyway ....
> 
> If you're ripping tyres on sharp rocks then the RR's are not the best choice..


Well I already ordered tubes so may upgrade in the future. We don't have a lot of rocks or thorns though.

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## Steve-XtC (Feb 7, 2016)

> I wanted to double check front sprocket size before pulling the trigger. I'm going to reuse the stock cranks for now, need a NW sprocket up front.





> Started ordering parts! Rocket Ron's on the way.
> 
> I found a set of SIDs for $100 locally. Was on the fence due to either needing a disk brake or a v-brake adaptor. Then I thought of my cruiser bmx and decided I'm going to do away with the front brake entirely, at least for now. The terrain we ride doesn't really need front brake but my son is typically grabbing that one. So he is going to go rear brake only for a while so he learns to use that properly.
> 
> ...


Sorry didn't read every thing on the thread but I'll give you the benefit of my experience* in terms of where I wasted money trying to save it....*

The cranks will be way way too long... somehow better to just bite the bullet and buy the NW once. You don't need to go mad but the Trailcraft square taper ones are pretty reasonable $$.. though I've just converted adult ones which is WAY easier than it sounds... (even new SRAM S600's are cheap but I did get a set of used Alivio's for <$20... )

Our sub $10 stem off eBay was a bargain (Wake)... only ditched it because he grew and needed a longer one.... the bars were $15 carbon off ebay... and have been in use and multiple crashes 2yrs later...

Converting SID's is either time consuming or expensive and probably both. 
I speak from experience....

If you group some RST F1rst's from Bikediscount with tyres etc. it makes the postage less of a factor but if you figure you don't need a front brake then I'd question spending on a suspension fork altogether!

If you are going one back brake though then the integrated shifter/brake can't have the distance between them adjusted. Its worth considering....

Jnr got really serious so I did end up spending more money eventually but some of the purchases I made trying to save money were just a waste of money... 
He's racing competitive DH now so the money on the SID's wasn't wasted... but for competitive XC they would have been complete overkill... and for kids competitive XC aged 6-8 you could EASILY get away with rigid forks... so for non competitive light XC type trails even more so....


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## sharp21 (Jul 25, 2014)

Some good advice, thanks. I'm going to go with separate brake and shifter so the reach can be properly adjusted, and will bite the bullet and do the 1x conversion properly.

What length cranks should I be looking at? I can get a Promax SQ-1 in 155mm or Origin8 in 150mm. I'm leaning to the Origin8's as it seems stupid to only go down by 10mm from stock.

Going to replace the BB while I'm at it. Thoughts on this one from Origin8?

The final step that I've been going back and forth on is relacing the wheels to big boy hubs and upgrading the rest of the drivetrain out back. But then that adds the cost of hubs, spokes, cassette AND RD. He just rides trails with his Dad, no racing or anything, so it seems like diminishing returns. Although I do _really _like wrenching on bikes!

Trouble with forks is that 24" rigids are almost as much as the SIDs I've got lined up. I did have a guy offer a Judy shox cheaper but I think that will be heavier?


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## sharp21 (Jul 25, 2014)

So my shopping cart consists of:
Handlebars
Grips
2 x brakes + levers + cables
Shimano Rapid Fire 7 spd shifter
Bottom Bracket
Crank, sprocket (38T), and bolts
New pedals
7spd chain
Park crank puller
BB remover

Am I missing anything? Should I go whole hog and throw in a new RD as well to replace the banged up old one?


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## Steve-XtC (Feb 7, 2016)

> What length cranks should I be looking at? I can get a Promax SQ-1 in 155mm or Origin8 in 150mm. I'm leaning to the Origin8's as it seems stupid to only go down by 10mm from stock.


Scroll to the very bottom of this page... it's the best size guide I've found. (They must have copied it from somewhere but I never found where) 
A very rough guide is something like 140mm for a kid just getting big enough for a 24"

https://highpath.co.uk/crank-shortening/

From above I take it your cranks are 165mm and the seem to have a standard 104 BCD just from the photo.

If this is the case AND you need about 140-145 you can shorten the ones you have for now. Once you remove the steel chainrings and replace with a NW they will drop a lot of weight. The Sq. Taper BB is still heavy... but depending what it is and the condition you can but a Shimano UN55 for $15 or so.... these are reasonably light and last forever (at least with a kids power) just take the old one out and inspect/weigh it... then you can decide if its worth it... you can also probably use a slightly shorter BB when you go 1x... and pull the outer ring closer as it no longer has to span 3 rings...



> Although I do really like wrenching on bikes!


Shortening your own requires a drill and taps (and a file and hacksaw). It's far easier than it sounds... and you can do it again and again. You don't need the best taps they are for steel cranks... but when you tap instead of 3 forwards/1 back I smear it with grease and 2 forwards then one back.

When you drill (I use metric) I use a 5mm pilot then a 8 or 9 then a 13mm ... 13mm is pretty close to the right size for 9/16ths but very slightly bigger... (its also about as big as you commonly get in most domestic chucks)

The very slightly bigger just gives a bit more holding for the steel pedals...

When you drill the pilot I started off (first time) with all sorts of fancy wooden jigs... it's really not needed... I stick a pedal in the original hole prior to cutting and then drill parallel... just stick it in a vice with some cloth to protect the cranks

When you drill the 13mm (or equivalent) there will be a LOT of torque when it beaks through. At this point the hole direction is done so I clamp some hardwood to the exit.

As you are drilling higher up where its slightly thicker the pedals won't need to screw into the far side... so you can clean it up after... just make sure the outside is square and flush (depending on cranks this might mean filing or angle grinding)

I usually cut before final tapping... I have been known to cheat and use a PCT bench saw... (the downside of this is generating heat because the Al alloy is heat treated) ... and it might also slightly distort your hole... so after I run the 13mm back through just to be sure.. and then tap it as described above.

Finally you can round off the ends with a file... this is easier if you cut a /-\ shape 
When I was at school my metalworking skills were only ever average....

If it all goes wrong it cost you $20 or so for the drillbit and taps.(assuming you have or can beg/borrow the drill, vice, file, hacksaw etc.)



> The final step that I've been going back and forth on is relacing the wheels to big boy hubs and upgrading the rest of the drivetrain out back. But then that adds the cost of hubs, spokes, cassette AND RD. He just rides trails with his Dad, no racing or anything, so it seems like diminishing returns.


Yeah, big warning... that how we started...  then one day we met another Dad and kid in a car park ... but your spot on.

If that is where it goes or you want to ride longer trails and bigger climbs etc. or even a specific type then you might change the whole bike (or not)? or spend more on this one etc.

I'd say maybe leave the forks as well for now.... they are springs so they are heavy but going down modifying is major engineering. They are kid specific so if you take em part and clean and regrease they should work despite being heavy.

At some point though you are going to need brakes...
Kids at this age progress frighteningly quickly..


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## sharp21 (Jul 25, 2014)

Thanks for the writeup! The only hesitation I'm having before submitting my order is that the short cranks from Sinz or Origin8 are 110BCD, so the smallest chainring I can find is 38T. 

Trailcraft cranks are the only ones in 104BCD, but another $30. I'm at $300 already and have hit my spending limit.


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## Steve-XtC (Feb 7, 2016)

Trailcraft cranks are the only ones in 104BCD, but another $30. I'm at $300 already and have hit my spending limit.

Handlebars
Grips
2 x brakes + levers + cables
Shimano Rapid Fire 7 spd shifter
Bottom Bracket
Crank, sprocket (38T), and bolts
New pedals
7spd chain
Park crank puller
BB remover

Bars I paid $20 or less.... grips I cut down some old ones of mine... the fact they had worn a bit thin was a bonus.
7 speed shifter, 6,7,8 chain and UN55 BB are cheap

Pedals we really splashed out.... I think around $35-$40 but these are Ti Axle weigh almost nothing. (AEST)

Park crank puller isn't that expensive... and sorta worth it over taking a risk on something that doesn't work right. (IMHO)

*That really only leaves the cranks.... *
If you own the other stuff then a drill bit and taps should cost you <$20
If its a 104 BCD then your choice of NW is bigger.... you can go down to 30T (much more realistic) and you will probably find one cheaper as you have way more options.

IMHO 38T is WAY too big... Jnr is a very strong rider and uses 34T in XC races for where speed but he uses a 32 with a big cog on back for normal riding.


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## alexbn921 (Mar 31, 2009)

Drilling and tapping your current cranks will cost you more in taps then buying new ones.
Get some 140mm 110bcd BMX square tapper crank arms and call it a day. I used an ultegtra 34 tooth that I got for $7. it's not NW, but there are no shift ramps and it works great. Kids gearing is different then ours and 34 is a nice sweet spot, unless your hills are super steep.

https://www.danscomp.com/products/452681/Skyline_RB20_Alloy_Crank_Arms.html

https://www.amazon.com/Shimano-Ulte...25188461&sr=8-6&keywords=shimano+ultegra+ring

don't forget chain ring bolts too.


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## rabitoblanco (Feb 21, 2017)

I'm going to go against the general 1x grain here, and say this-- take off the outer ring (replace with $12 BBG bashguard), then see how the riding goes in your local trails with the 22/32 that's currently on there. 
My son's a pretty strong rider for his age, and a 30 would be a single number I would choose-- surely nothing as large as a 38, and even at 34, he'd be just on the large ring in the back the whole time.

Here's the thing-- you want them to have the flexibility for some speed, and also for some play/fun--where they can pull up their front wheel etc. with cranking power, and the larger ring will make the bike less fun.

-Ridwan



sharp21 said:


> Thanks for the writeup! The only hesitation I'm having before submitting my order is that the short cranks from Sinz or Origin8 are 110BCD, so the smallest chainring I can find is 38T.
> 
> Trailcraft cranks are the only ones in 104BCD, but another $30. I'm at $300 already and have hit my spending limit.


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## Steve-XtC (Feb 7, 2016)

X-Tools Pro Pedal Tap | Chain Reaction Cycles

Pedal Taps are $12 each... (one left and one right) and these are the X-Pro ones which are far from the cheapest but easy to order and free delivery.



> Kids gearing is different then ours and 34 is a nice sweet spot, unless your hills are super steep.


Yep and you can get half the story here: 
BikeCalc.com - Bicycle Gear Meters of Development Chart
but the other half is the weight of the bike compared to the weight of the rider....

It's not so much short steep hills where the gearing comes in (from experience). Jnr runs a 34T and a 11-32 on the back for XC races but *these are only 20-30 mins *and he is on a podium with kids up to 10 riding 27.5 bikes.

Riding closed circuit roads they just adopted new rules last year (copied from the US and converted into metric) the maximum gearing allowed in competitive racing is based on one full pedal stroke 
Cat Max Progression
Youth D (U10) 5.40m (17' 8 1/2")
Youth E (U8) 5.10m (16' 8 3/4")

With a 34T on the front and a 2.25" size 24" tyre that basically means his 11-16 cogs have to be locked out with limit screws as they are considered 'unsuitable'. 
(personally I think this is a load of crap but I'm just giving context - he obviously uses bigger gears in XC where the rules don't apply)

The thing is when we go out family riding his bike weighs proportionately more of his bodyweight than mine does.

I actually own a super heavy steel framed 26 wheel bike with a 34T and a 11-32 but even this is nowhere near the same fraction of my body weight as his sub 19lb race bike....To be honest I never weighed my heavy steel geared jump bike... but it weighs a LOT and riding 15-25 miles off road at the kids speed I'm absolutely dying by the time I get back ... this is part of the purpose of this bike so that's to be expected. The point I'm trying to make is gearing and weight both quickly add up to fatigue and lack of fun... In this case I'm deliberately doing it to myself but I can say there are times it's just not fun and I'm purely doing it for fitness. The other half of the reason is its fun bike to jump... the sad thing is by the time I get to the top of the hills I'm struggling to breathe let alone enjoy some cool jumps...

Going out for fun family rides is just easier with some easier gears... we go much further / longer before it stops being fun.


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## Steve-XtC (Feb 7, 2016)

> Here's the thing-- you want them to have the flexibility for some speed, and also for some play/fun--where they can pull up their front wheel etc. with cranking power, and the larger ring will make the bike less fun.


We just cross posted.... but yep.... if the idea is FUN



> I'm going to go against the general 1x grain here, and say this-- take off the outer ring (replace with $12 BBG bashguard), then see how the riding goes in your local trails with the 22/32 that's currently on there.
> My son's a pretty strong rider for his age, and a 30 would be a single number I would choose-- surely nothing as large as a 38, and even at 34, he'd be just on the large ring in the back the whole time.


Again we cross posted except that's a pretty smart idea.... you don't even need the bash guard if you can switch the 3x to 2x.... (which most Shimano thumb shifters have a switch somewhere to do...)

My money is on the 30T being spot on... possibly 32T


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## sharp21 (Jul 25, 2014)

alexbn921 said:


> Drilling and tapping your current cranks will cost you more in taps then buying new ones.
> Get some 140mm 110bcd BMX square tapper crank arms and call it a day. I used an ultegtra 34 tooth that I got for $7. it's not NW, but there are no shift ramps and it works great. Kids gearing is different then ours and 34 is a nice sweet spot, unless your hills are super steep.
> 
> https://www.danscomp.com/products/452681/Skyline_RB20_Alloy_Crank_Arms.html
> ...


Those links really helped, thanks. I was having trouble sourcing anything under $50, and couldn't find a 34T tooth sprocket. Cranks in 104BDC are even more expensive at $80. Would have preferred 32T but this is going to work out fine.

All parts ordered! I'm up to $400 in parts, plus $200 for the bike. It is now officially worth more than my bike...

Next up, the build!


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## rabitoblanco (Feb 21, 2017)

sharp21 said:


> All parts ordered! I'm up to $400 in parts, plus $200 for the bike. It is now officially worth more than my bike...


Wait a second-- wasn't the budget $300 for parts?!  haha, it's somehow a lot easier to spend on them than yourself, isn't it? Looking forward to the build!

What brakes did you go with?


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## thesmokingman (Jan 17, 2009)

Me: Babe, I'm gonna buy so and so for my bike. 
Her: What!?
Me: Gonna buy a new frame for the the kid.
Her: OK!


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## sharp21 (Jul 25, 2014)

rabitoblanco said:


> Wait a second-- wasn't the budget $300 for parts?!  haha, it's somehow a lot easier to spend on them than yourself, isn't it? Looking forward to the build!
> 
> What brakes did you go with?


Haha yup!

Went with new v-brakes levers and cables. Plenty of power for the kiddo

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## sharp21 (Jul 25, 2014)

Let the fun and games begin

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## jmossbarger (Oct 30, 2013)

That's funny! I took a similar picture before my build!










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## rabitoblanco (Feb 21, 2017)

Nice! 

I'm amazed y'all have the patience to wait to install all that goodness when it arrives?! 

Rowan's RaceFace Chesters are already worn at the edges, and most of the new parts aren't even here! 

Good luck putting it all together!


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## sharp21 (Jul 25, 2014)

rabitoblanco said:


> Nice!
> 
> I'm amazed y'all have the patience to wait to install all that goodness when it arrives?!
> 
> ...


Well I ordered and then went to work for 3 weeks, so it was all waiting for me when I got home!

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## jmossbarger (Oct 30, 2013)

Similar situation here. I ordered most of it and then started a bathroom project. Had to get the bathroom functioning before bike work! 


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## sharp21 (Jul 25, 2014)

Got the new Rocket Ron’s onto the front wheel. Started on the back but cannot get the free cassette removed for the life of me! I’ve got the proper tool but that thing won’t budge. 

Any ideas?


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## alexbn921 (Mar 31, 2009)

I use an air impact to zip off the really stuck stuff.


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## sharp21 (Jul 25, 2014)

Got it! Took my biggest wrench and my biggest hammer. 









Out with the old and in with the new!









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## sharp21 (Jul 25, 2014)

Wheels complete! Schwalbe Rocket Ron's with Kenda tubes in Alex Ace 20s. New Shimano 7 speed freewheel, and shiny red skewers to finish them off.










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## sharp21 (Jul 25, 2014)

Getting close. Stripped and cleaned.










Drivetrain swapped.





































Carbon bars shortened, with new shifter and rear brake installed. All new cables.










Drivetrain buttoned up.










We'd to adjust the RD and brake tomorrow, then time for a shakedown ride.










Very happy with the progress and my son loves it. Maybe would have gone with white pedals if I could do it again... Going to leave the front brake off for now. I'd still like to swap the front fork out, but I'm done after that. I swear.

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## rabitoblanco (Feb 21, 2017)

sharp21 said:


> ...*and my son loves it*...


The only part that matters!

Looks great, man! I've never taken a bike all the way down like that-- perhaps the next one!

Question--what shifter did you go with?

I just received the Microshift push/push shifter for Rowan's bike and it just seems very heavy.


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## sharp21 (Jul 25, 2014)

rabitoblanco said:


> The only part that matters!
> 
> Looks great, man! I've never taken a bike all the way down like that-- perhaps the next one!
> 
> ...


It's a Shimano 7 speed trigger shifter. It works so well that I'm going to get one for my daughters bike next.

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## TJJohnny (4 mo ago)

Is there a stock spring that I can swap out for the rear shock? My son cannot even flex this thing at around 70 lbs. Would love to swap in a lower spring rate.


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