Any options apart from a new crankset?

fury21

Alfine Crankset:

Seems a stripped plastic crank arm fixing-bolt/cap (possibly from original build) meant I was over-tightening the side bolts (1 and 3 respectively here) to stop the play in the crank arm.

When the left crank started slipping, my LBS fitted a new alloy crank cap, but the problem has returned. Appears there simply isn't enough bite left in the teeth...






I believe my only option is to buy a new crankset, but thought I'd check here before spending the money.

nicklouse

new cranks.

never seen them that bad.

fury21

:oops:

thanks.

supersonic

The plastic 'fixing' bolt does not fix it to the crank arm - it preloads the bearings.

will3

How the heck did you manage that?

supersonic

All I can think of is because of the play from not being able to preload the bearings, the OP mistook this for loose crank arms and over tightened.

will3

Overtightening did that? Looks more like undertightening leading to slippage of the spline to me, :? Don't they have that plastic insert thingy that goes in the split of the crank to stop you over-tightening?

supersonic

The overtighning could have destroyed the splines I guess, the OP mentioned he overtightened.

nicklouse

i am thinking that if the crank was lose and only the preload cap was tightened and the clamping bolts were not then the "chatter" seen could happen.

But i would have expected the LBS to have checked before fitting the new preload bolt.

fury21

:oops:

All I can think of is because of the play from not being able to preload the bearings, the OP mistook this for loose crank arms and over tightened.

yup.

I didn't know the purpose of the fixing bolt and had never touched it (until recently I didn't even have the right tool for it). I can only guess it got stripped during the original build (a certain national chain)

I didn't really notice any problem until going clipless when I found I had play in the left crank and needed (as I thought) to tighten the side bolts fairly regularly. Despite (or now more likely, because of) this I started getting noisy creaks from the crank...

First trip to LBS they found the stripped plastic bolt (which they had never seen before) and they wanted to replace with alloy but didn't have it in stock, but they got things put back together to keep me going. (I think they said they used the fixing bolt from another bike to put it all together then substituted it for my worn one). Wear on the teeth was noticeable but not as bad as it is now.

2 commutes later, the crank rotated about 90 degrees, & not in a good way, before it came off completely (whilst I was still clipped in, of course).

Back to the shop, they had the alloy bolts in stock but did warn me that if the teeth were too worn to hold, it'd be a new crankset. Everything ran fine for about a week, then the creak returned and finally the crank arm just gave again and I had to ride home one-legged.

So bought the tool for the fixing bolt, took everything apart myself and here we are.


Morale of this tale: If in doubt, go to LBS and sooner rather than later.

supersonic

I think Shimano calling it the 'fixing' bolt is misleading.