Loose crank

[dallas95]

My xtr (M951) drive side crank keeps working loose. Other side is fine so after tightening it again today I thought I would ask if anyone has any suggestions as to how I can stop it working loose again. It only lasts about 3 miles before it starts to work loose. I have another bb I was going to try but thought I'd post here before getting the tools out.

 

[Bullpup]

Watching this with interest - before I hunt for my tube of blue Loctite.

 

[DeletedUser006]

Interesting, My dad has the same cranks on his new bike and both sides do the same as yours, so will watch with interest if ok maybe its common to these M95X cranks

Im guessing its a crank bolt issue or a loctite cure :?

 

[captaincosmic]

sure you have the right length bolts and are using washers too ???
I had the same prob then got some shorter bolt with nice fat washers and its fixed.
Maybe when you are tightening the existing ones up the get so far and then no amount of torque will tighten them any more ? It is because the bolt has reached the end of the thread and with a shorter one or fatter washer you can keep tightening away.

Or use threadlock lol

 

[dallas95]

The bolts are the original and they have a thin washer. They are the same both sides so it just seems a bit odd that only the drive side comes loose. The bb is a few years old so maybe the threads are worn. I may try the swap. I have some threadlock but someone told me not to use it as if I get the bolts tight I won't get them out again. :?

 

[Pogo]

Sounds like the square taper on the crank has worn.
Take off the crank and examine the taper( the inside face), it should be nice and square with four good straight edges.

My guess is you will find that one or more of the faces will be worn, causing the crank to push further onto the axle than it should, hence you cannot secure it because the crank bolts bottom out onto the axle and not the crank.

 

[djoptix]

Tighten it up incredibly, insanely tight. If you don't, once it's worked loose a few times, the alloy of the crank will get deformed and you'll never get it tight again.

 

[Bike Hoarder]

Tapers of the crank arm are no longer square with the taper on the BB axle...

Seen this a lot with cheap bikes, especially the LH arm. Never seen it with more expensive cranks.

Unfortunately, the more you ride it with it working loose, the more it will happen. The rocking motion of it working loose is making it worse and worse. I don't know of any action that will stop this, loctite the bolts may help, over tightening it will only stretch the taper of the crank arm - not making it a tighter fit.

The only option is replacing in the arm in my experience.

(i really should learn to type faster........... :roll: )

 

[jonboy]

If you don't know what you are talking about then don't comment, as proved by the above 3 posts. :roll:

That crankset is not a square taper style , it fits on to hollow axle Octalink V1 type bottom bracket.

Really need to see pictures of the back of the crank arm and the end of the BB to be able to diagnose why they are coming loose.

 

[DeletedUser006]

I presume there is some sort of taper but the XTR cranks use a ocatlink bb that is only XTR compatible, no square tapers involved on my dads setup :?