Shortening your cranks

[philipshaw]

Correct.

Thanks again

 

[surlyrides]

I was really happy to see this thread as I have been continually irked by the length of the cranks on my altitude power play...

Reading the op's first post, The question that comes to my mind is, can't I just take my existing rf crank arms to a machine shop to be drilled and tapped down to 150mm? This wouldn't require purchasing any new parts. Am I missing something? I have the C70 altitude.

Thanks in advance!

 

[A06]

I was really happy to see this thread as I have been continually irked by the length of the cranks on my altitude power play...

Reading the op's first post, The question that comes to my mind is, can't I just take my existing rf crank arms to a machine shop to be drilled and tapped down to 150mm? This wouldn't require purchasing any new parts. Am I missing something? I have the C70 altitude.

Thanks in advance!

That was literally in the very first post of the thread.

Yes you can machine them depending on which crank arms you have, Atlas have enough material to go to 155mm from the stock length but I think 150 will be risky. If you want 150mm you would need to start with 165's.

Thats the route I'm going as its an incremental process. 165's are a welcome improvement for sure but eventually I'll probably go to 155-150 but to be honest I'm stalling to see if RM or RF come up with a better solution in which case I'd sell the 165's to fund the purchase of hopefully a shorter drop in option.

 

[surlyrides]

That was literally in the very first post of the thread.

Yes you can machine them depending on which crank arms you have, Atlas have enough material to go to 155mm from the stock length but I think 150 will be risky. If you want 150mm you would need to start with 165's.

Thats the route I'm going as its an incremental process. 165's are a welcome improvement for sure but eventually I'll probably go to 155-150 but to be honest I'm stalling to see if RM or RF come up with a better solution in which case I'd sell the 165's to fund the purchase of hopefully a shorter drop in option.

Thank you. The first post discusses switching crank arms rather than machining the stock crank arms. My question was specifically about the stock crank arms without purchasing new crank arms or any other parts.

I think that the answer to my question is " yes " ... But if anyone wants to chime in on using the stock crank arms without replacing any parts and just machining the existing ones shorter, that's what I'm curious about specifically.

 

[S13]

It doesnt matter if the cranks are new or came on your bike pre-installed. What matters is which type it is. The more expensive Atlas or Turbine cranks can be drilled down, the cheaper Ride cranks cannot.

 

[KAMTHETANK]

Any recommendations for where to get cranks drilled and shortened and what I should expect to pay?

 

[KAMTHETANK]

Over the past weeks ive been gathering information on how to shorten the cranks on Rocky Mountain Powerplay bikes. I hope this info helps some of you with this quite complicated task.

So in order to get shorter cranks than the stock 170's (or if you are lucky the 165) there are a couple of solutions, both involve getting either a RaceFace Atlas or Turbine crank set.

So to start with you either have one of 2 situations:
1. You already have the bigger 30mm axle cranks installed on your bike (probably Turbine)
2. You have the smaller 24mm axle Ride cranks


The solution for situation 1 is simplest. Buy a set of Atlas cranks in your preferred length. Shortest you can go is 165mm. If you buy the longer 175mm you can drill them down to 155. You can also drill Turbine cranks shorter, if you prefer that route. 170 to 150 is possible and 175 to 155 as well. Turbine is sold out everywhere so might not be the easiest option. Turbine does not come shorter than 170.
After you get your new and optionally machined cranks, fit them with the original spindle that came with your bike. It should be a RF149 spindle (149mm end-to-end spindle length). Also fit the original clutch spider assembly with the 30mm locking ring. Install on bike and you are done!

Now situation 2 is more complicated, because you dont have the parts to use the 30mm cranks, and re-drilling the original Ride cranks is not recommended due to the internal structure. So the only option is to first install a 30mm bottom bracket (for example a BB92 Double Row CINCH 30mm with 92mm shell width). Then you need to buy the correct length 30mm spindle. Rocky Mountain advises the RF149 (149mm end-to-end spindle length), and that is what most people seem to use. You can buy these spindle kits at several web shops. You also need to contact RM or you local RM dealer to get a hold of the 30mm locking ring for the spider clutch. For the remainder, the same applies as for solution nr 1; get a set of Atlas (or Turbine) cranks, optionally drill them to desired length, fit cranks with the new correct sized spindle, install original clutch spider with new 30mm locking ring, and you are good to go.

One point to remark is that you can also buy Atlas cranks in so called "83mm" variation. On the Raceface website this shows as "Spindle Size 151". These cranks come with the 151mm RF151DH spindle already attached to it. Now im not sure these will fit the bike, but the difference is only 2mm compared to the recommended RF149 spindle, so perhaps minor enough that you can adjust the free play with free play adjustment ring, or perhaps a spacer. This would save you the hassle to buy a separate spindle kit for another 100 bucks.

This document from Race Face provides you with information on the available spindle sizes.
Note that it says:
• Spindles with suffix “BM” or “DH” (eg.RF136DH) are compatible with SixC and Atlas cranks only
• Spindles without “BM” or “DH” suffix (eg. RF134) are compatible with Next R, Next SL and Turbine cranks only

So according to the document the Atlas crank should not be compatible with the RF149 spindle, but is compatible with the RF151DH spindle. However on the facebook group Norman mentions he has successfully used the RF149 spindle with his drilled Atlas cranks without any problems.

Atlas cranks drilled from 175 to 155 by Norman:

Turbine cranks drilled from 170 to 150 by Andy:

According to Andy, drilling 175 Turbine to 155 is also possible.

So there you have it. I have not verified any of these solutions, so i cannot guarantee the information provided here is correct. But hopefully it helps you get started.

Where'd you get this done?!

 

[S13]

Where'd you get this done?!

Be more specific?

 

[KAMTHETANK]

Be more specific?

Where did you get your cranks shortened and redrilled?

 

[S13]

Where did you get your cranks shortened and redrilled?

I didnt. Did you even read the post?

 

[KAMTHETANK]

Yeah I read the thread. The first post has pictures of cranks that have been drilled and shortened. I'm trying to get some help on resources for this.

 

[S13]

Well like i said in the original post, these are from Norman and Andy on the facebook group. Maybe they can point you in the right direction.

 

[A06]

Yeah I read the thread. The first post has pictures of cranks that have been drilled and shortened. I'm trying to get some help on resources for this.

Short Bicycle Cranks