[Closed] loose cranks..

it should be the pinch bolts (in the crank arms) holding it all together the preload thing is really just to set the initial tightness (like the top cap in a headset - it's the stem bolts that hold it together).

Don't those cranks have pinch bolts on the non-drive side that are the main means of attaching the cranks? is it these that are working loose?

You want to try doing up the pinch bolts. These cranks are designed so they should never come loose when fitted properly.

No, these are staying tight, I've tried them REALLY tight, and it made no difference, plus i have to undo them each time to tighten the preload thingy. THe preloader actually comes undone...

So the pinch bolts are tight, yet the crank is still loose on the BB axle?
The preload cap is pretty much irrelevant once the pinch bolts are done up.
If the crank is loose when the bolts are tight, either the crank splines have been damaged or possibly you've got the wrong type of BB?

After the pre-loader has come undone, do the cranks then slip off?

I've had this before and it was because I'd been a ****wit and not installed the cranks correctly the first time- it was all to do with the wrong spacing on my chaindevice which meant the non-drive side crank didn't have enough axle to latch onto. In that instance, I had managed to shear off the splines on the inside of the non-drive crank arm. It still fitted onto the axle, but there was nothing to latch onto.

Check you've not done the same thing and then don't feel bad, you're not the only ****wit to have done this 😀

Right so the cranks arnt loose then. Bit of threadlock or PTFE should do the trick. Not too much or it will be too tight when you come to preload them next.

Or alternatively just remove it. It only has a use when fitting the cranks and is just extra weight the rest of the time.

Hmm, i think i'll try some ptfe tape on the thread of the preload thingy, i have some in my toolbox... To clarify, they are tight and stay that way for around 10 mins of riding, then come loose.

Thinking about it I may just buy a new chainset though, as i'll need a new bb, and chainrings anyway in a few hundred miles....

To clarify, they are tight and stay that way for around 10 mins of riding, then come loose.

That doesn't clarify things. Is it JUST the preload bolt that comes loose or is the NDS crank loose too?

*confused*

1) the preloader comes undone after a few minutes of riding
2) the pinch bolts stay done up tight
3) the LH cranks slides off the axle

?

if you're having to use the pre-loader to hold the cranks on you've done something wrong when fitting - I often run cranks without the preload cap on them and don't have any problems.

ALmost certainly then you've damaged the splines on the inside of the non-drive crank arm.

I think the consensus if opinion is your crank splines are now borked! Sorry.

I had this with a set of Truvativs (which seem to fix in a similar way). I cleaned and de-greased as best I could, then covered the whole bastarding thing in "No More Nails", did it up properly firmly and left it to set for a bit. So far this solution has been trouble-free, although I anticipate having to use a saw and some dynamite if I ever want to remove them. 🙂