# Changing the crank on a 2015 Giant XTC Jr SL to a 1X question?



## bglimpse (May 19, 2004)

Greetings,

Just picked up a 2015 Giant XTC Jr SL for my son. It has the 3x crank from the factory and a 8 speed HG31 11x34 stock. I'd like to change out the crank to the TrailCraft 1x 32t. I've been talking with TrailCraft and the issue is the TC chainring is designed for 10/11 speed chains. 

Will I have issues with the chain coming off if I'm using an 8 speed chain? 

Will a chain guide solve the issue?

Are there other 1X cranksets to investigate?

Thanks.


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## watts888 (Oct 2, 2012)

why change the crank? why not just remove the 3 rings and throw on a raceface 30T narrow wide ($45)? It will work with 8-speed chains, although it will be a little sloppy. 

Easiest alternative is to remove the granny and big ring, keep the 32t middle ring and put on a bashguard ($10-15) (or shorter chainring bolts($5) or chainring bolt spacers ($5)). I've run 8-speed chains on a standard chainring and only time I dropped a chain was on really rocky bouncy stuff when the chain was skewed (chain in the smallest ring out back and almost no tension on the derailure).

Side note, I'd also recommend changing that rear cassette from the 11-34 megarange to a shimano 11-32 cassette. Much smoother transition for the last couple gears, and with a 24" tire and 30T chainring, how often will he need the megarange.


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## bglimpse (May 19, 2004)

Didn't even think of that, I'll need to take a look when I get home. I thought I had read somewhere that the rings were riveted on, but looking at the photos the 42t is definitely bolted on. Worst case, the 22t is riveted and I can just leave it on there and remove the derailleur. I'll look into the cassette as well, it states its a freewheel but it may be a true cassette. Thanks for the help.


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## Steve-XtC (Feb 7, 2016)

watts888 said:


> why change the crank?


Because if the kid was big enough to be able to use that crank they would be riding a 26er.


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## Steve-XtC (Feb 7, 2016)

bglimpse said:


> Didn't even think of that, I'll need to take a look when I get home. I thought I had read somewhere that the rings were riveted on, but looking at the photos the 42t is definitely bolted on. Worst case, the 22t is riveted and I can just leave it on there and remove the derailleur. I'll look into the cassette as well, it states its a freewheel but it may be a true cassette. Thanks for the help.


If its really a cassette then I'd rip off the cranks and cassette and stick on a XT cassette and 10 sp shifters.

My kid runs a 30T narrow wide with a 11-36 but will be adding a 40T expander soon. (Once he gets the hang of 10 gears and is using them properly)

For where we are the 30/36 is barely adequate.


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## stom_m3 (Jun 28, 2011)

Steve-XtC said:


> If its really a cassette then I'd rip off the cranks and cassette and stick on a XT cassette and 10 sp shifters.
> 
> My kid runs a 30T narrow wide with a 11-36 but will be adding a 40T expander soon. (Once he gets the hang of 10 gears and is using them properly)
> 
> For where we are the 30/36 is barely adequate.


Hi Steve, I would go straight to XT 11spd drivetrain instead of the expander. The price is a wash and he will gain an extra gear. The new XT 8000 stuff is actually decently priced. By the time you buy the expander and 17t cog, the price will be the same or more. I should have done that with my sons bike but at the time when I was buying all of the parts, Shimano was just starting to roll the 11spd stuff out.


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## LewisQC (Jul 3, 2013)

. I've been talking with TrailCraft and the issue is the TC chainring is designed for 10/11 speed chains. 

For what I know, you can use 10 speed chain on a 8 speed cassette if you want to use trailcraft cranks... 

I'm currently looking for a 24" bike for my daughter and drivetrain choices are sometime strange. 

You can buy a Shimano Crank S600 and drill some new hole at 150mm and cut the excess (if the bb is square tapper)...


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## Steve-XtC (Feb 7, 2016)

stom_m3 said:


> Hi Steve, I would go straight to XT 11spd drivetrain instead of the expander. The price is a wash and he will gain an extra gear. The new XT 8000 stuff is actually decently priced. By the time you buy the expander and 17t cog, the price will be the same or more. I should have done that with my sons bike but at the time when I was buying all of the parts, Shimano was just starting to roll the 11spd stuff out.


Good point.... I'm a bit behind maybe. (Perhaps partly because I'm in the UK and we seem to lag a bit)
Beauty of the M780 stuff at the moment (in the UK) is loads of nearly new being sold off as people upgrade to 1x11.

My kids bike is a mix of new/eBay used and eBay new sold off cheap.
(The Rear brake is SLX because it was going new/boxed for £15 with everything but the rotor)
Rearmech is a used barely used XT Shadow+ (I think about the same price)
Front Brake/Shifter (XT 780) is new because CRC were doing about 40%-50% off... (due to the M8000 coming out)

but your right that the M8000 stuff is more readily available/less premium/decently priced ... perhaps what I should have done was upgrade my bike to a 1x11 and donate the 10sp to the little one!

p.s Got an expander for £15 and 13t lockring for £0.5 (ebay no bids).... postage cost more than the lockring... so I'm planning on just ditching the 13 for now rather than taking out the 17. (Should be fast enough for a 6yr old and if its not I'm not having him go faster than me)

(Won't really miss the 13 as he only rides this bike offroad/single track as we kept his 20" for school/other since Mum can't work out a quick release and it fits in her station wagon wheels on... and it's not a disaster if its stolen)


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## Steve-XtC (Feb 7, 2016)

LewisQC said:


> . I've been talking with TrailCraft and the issue is the TC chainring is designed for 10/11 speed chains.
> 
> For what I know, you can use 10 speed chain on a 8 speed cassette if you want to use trailcraft cranks...
> 
> I'm currently looking for a 24" bike for my daughter and drivetrain choices are sometime strange.


That definitely an understatement!

Either: 
A) Decide 175mm is correct for a 5'10-6' person then work out what ratio of that fits a 4' kid... 
OR

B) use the chart on 
Crank Length Calculation - Highpath Engineering Ltd

Either way I haven't seen any mainstream kids bikes with even close. 
See Stom's thread on the Carbon 26er... he's just put 145mm cranks and his kids big enough to ride a 26er...
http://forums.mtbr.com/families-riding-kids/carbon-frame-xs-26-build-1000095.html#post12531793

I'm now thinking I should have actually gone shorter than the 142.5mm... but 155mm+ on a 24err is ridiculous... 165mm is beyond ridiculous

Neither is it really much more expensive to go 1x11 than 3x8...



> You can buy a Shimano Crank S600 and drill some new hole at 150mm and cut the excess (if the bb is square tapper)...


It's SRAM S600 (not Shimano :nono - just a little pedantry but more importantly its really quite easy.... (or nowhere near as hard as you might think anyway)

GrayJay posted a guide on here and I followed it.

I drilled out something like 5mm then 10mm then 13mm then tapped it with 9/16th pedal threads .. just kept lots of grease in the hole as I tapped it...


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## LewisQC (Jul 3, 2013)

It's SRAM S600 (not Shimano :nono - just a little pedantry but more importantly its really quite easy.... (or nowhere near as hard as you might think anyway)

GrayJay posted a guide on here and I followed it.

I drilled out something like 5mm then 10mm then 13mm then tapped it with 9/16th pedal threads .. just kept lots of grease in the hole as I tapped it...[/QUOTE]

Oups my mistake... Going crazy about all those kids bikes and potential upgrades!!! I asked a machinerie shop if they would drill the cranks for me but maybe I should try it myself...

I'm looking for a bike with a spinner fork... Not to many choices around here: Norco Charger, Opus Fever 24. I will check on a used Opus tomorrow...


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## GrayJay (May 16, 2011)

Should anyone need it, my benchtop hand-held crank shortening writeup is down toward bottom of thread;
http://forums.mtbr.com/families-riding-kids/sx-26-trek-4500-kid-build-961774.html

back to the OP question; it should be no problem to use an 8-speed chain on a 10-speed 1x crank. A 10-speed specific crank with multiple chainrings has slightly less space between the chainrings because the outside width of a 10X chain is narrower than and 8X chain. The inside plate width of the chain and the pitch of the chains are the same so the fit on the 10-speed 1X chainring fine. Worse case, if you use an outer bashring in place of the large chainring and the wider 8x chain rubs, use washers to space the bashring out slightly.


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## Steve-XtC (Feb 7, 2016)

LewisQC said:


> Oups my mistake... Going crazy about all those kids bikes and potential upgrades!!! I asked a machinerie shop if they would drill the cranks for me but maybe I should try it myself...


I used a hand held rechargeable (though good quality) drill. Really easy, just control the speed or you melt the alloy. I also have a vice which definitely helps but you could secure them to wood and stand on it.

I thought it would be harder but

Didn't try the spinner but 
The RST air work very very well.

I have Fox float factory 100mm on 27.5's and the 24 inch RST seem to work better scale wise ... I have to say very impressed, I got the kids bike because of them but they have exceeded expectations.

I'm looking for a bike with a spinner fork... Not to many choices around here: Norco Charger, Opus Fever 24. I will check on a used Opus tomorrow...[/QUOTE]


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## bglimpse (May 19, 2004)

Good discussion, lots of info. I checked tonight, the chain rings are bolted on not riveted. That's where I will start. It is a true cassette, that will get upgraded as well. Dang nice bike from what I can tell. I can see myself falling into the upgrade game quickly, he better ride the wheels off of this bike


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## Steve-XtC (Feb 7, 2016)

bglimpse said:


> Good discussion, lots of info. I checked tonight, the chain rings are bolted on not riveted. That's where I will start. It is a true cassette, that will get upgraded as well. Dang nice bike from what I can tell. I can see myself falling into the upgrade game quickly, he better ride the wheels off of this bike


My advice if do it all at once.

i know it's always a gamble with kids ... He might take up other hobbies in 6 mo.
however, they will only fit on that frame 2-3 years max. so better to see the max use of any upgrades than wait and then lose a year on the investment

like stom said 1x11 is easy now ...you just need rear mech, cassette and shifter combined with a narrow wide chain ring. To buy that you need to measure the BCD of the big ring bolts. It's probably 104mm

you can only shorten non hollow cranks.... Btw


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