Can I shorten carbon cranks?

[mountainfun]

Hi

I have RaceFace SIXC carbon cranks, 170mm.  Awesome, except that the pedal insert has come loose.  (Thread not stripped.)  Apparently that cannot be fixed, but any comments on that also welcome.

What I was thinking is whether I can go extreme and shorten the cranks to say 162,5.  This would involve cutting etc.. It would need to be done by a very seasoned carbon expert.  

I'm sure the right answer is "no", for various reasons, but I thought worth a shot.

Thanks

JL

Edited August 24, 2021 by mountainfun

[Mamil]

I'm no carbon expert at all but considering the cranks are one of the parts of the bike that take the most pressure I would be disinclined to trust my well being to something that had been so modified.

Watching with interest for the proper bike people replies

[lechatnoir]

I'm with Mamil. Rather take the proper route and get new cranks. Whatever savings you have upfront are likely to be horribly offset if, or likely WHEN, the crank fails. I'm not an expert on carbon cranks, but I am an expert on Youtube moments and this is surely one waiting to happen

[Stavros94]

@mountainfunpost a picture if possible ? 

[DieselnDust]

One would have to be familiar with the detailed design of the crank to make a meaningful comment here. You may want to consult with the caron repair experts.

By way of example, if the insert is bonded into the carbon arm it may be possible to move it and reconstruct the bonding area in the new location you require.

If the pedal thread is tapped into a aluminium spine inside the crank then that threaded section  will have to be retapped in the new location. Since its typically a 9/16 x 20tpi imperial thread the new thread will have to be tapped at least 20mm away so already the crank is a lot shorter than you require.

Edited August 24, 2021 by DieselnDust

[TNT1]

25 minutes ago, mountainfun said:

Hi

I have RaceFace SIXC carbon cranks, 170mm.  Awesome, except that the pedal insert has come loose.  (Thread not stripped.)  Apparently that cannot be fixed, but any comments on that also welcome.

Why can't that be fixed?

That would be first prize, take it to one of the specialist carbon repair places and see?

[ChunkyMonkey]

Please put your first ride on GoPro….. after shortening the cranks…

I need to see this….

????????

[RobertWhitehead]

I believe anything can be done and or fixed, my question is just whether or not it's going to be beneficial. I mean there's sooooo many other factors to consider, makes me wonder

[mountainfun]

Thanks for all the comments, I really appreciate the quick replies.

I'm on the same page, just wanted to see if any other options.

I did speak to one of the carbon experts, and the advice corresponds!

 

[mountainfun]

[mountainfun]

[BogusOne]

I have fixed many cranks in the past. Some with great success still in use after years of use, some not so successful. All depends on the user or intended use.

Can it be done? Most definitely! Would I recommend it, definitely not, Not worth the effort or possible injury afterwards should anything go wrong. Can it be shortened? Most definitely. Would i Recommend it, possibly... Would I do it? Hell no.  Just for the sake of having carbon cranks absolutely not. Plenty of cheaper brand new options available in alu that is just as good....

If you absolutely must have it shortened speak to Greame Kidson @CarbonNinja He is the only one that I would recommend to shorten carbon cranks. I know he has shortened cranks successfully in the past ????

[Jewbacca]

2 minutes ago, BogusOne said:

I have fixed many cranks in the past. Some with great success still in use after years of use, some not so successful. All depends on the user or intended use.

Can it be done? Most definitely! Would I recommend it, definitely not, Not worth the effort or possible injury afterwards should anything go wrong. Can it be shortened? Most definitely. Would i Recommend it, possibly... Would I do it? Hell no.  Just for the sake of having carbon cranks absolutely not. Plenty of cheaper brand new options available in alu that is just as good....

If you absolutely must have it shortened speak to Greame Kidson @CarbonNinja He is the only one that I would recommend to shorten carbon cranks. I know he has shortened cranks successfully in the past ????

I was in the middle of recommending Graeme when your reply popped up!

[JA-Q001]

Do you want to shorten just to save the crank?

Shortening is a very complicated and laboursome job. You cannot just drill a hole and tap it.

It is quite easy and safe to just fix the loose insert.

the hardest is cleaning the cavity, then drilling a hole to inject resin into the cavity formed by the loose insert and then keeping it aligned while setting, so that your pedal does not have a wobble.

Graeme can fix it back to perfect for you, check his instagram, he has done it loads before.

And PS, stop using crank boots.

 

Edited August 24, 2021 by JA-Q001

[TheoG]

15 minutes ago, JA-Q001 said:

Do you want to shorten just to save the crank?

Shortening is a very complicated and laboursome job. You cannot just drill a hole and tap it.

It is quite easy and safe to just fix the loose insert.

the hardest is cleaning the cavity, then drilling a hole to inject resin into the cavity formed by the loose insert and then keeping it aligned while setting, so that your pedal does not have a wobble.

Graeme can fix it back to perfect for you, check his instagram, he has done it loads before.

And PS, stop using crank boots.

 

Agree.  The insert was bonded in there originally anyway.  No reason why its not possible for a carbon expert to build up and bond it in again.

[stefmeister]

Whenever I read something about Raceface carbon cranks, it's about them failing.