Originally Posted by
H3llM4rine
The cranks are two weeks old. They were new when I got them. I also think it's too early to think that the cranks are broken.
Sadly, no. It is not too early.
The taper in a crank must be a very precise fit with the taper on the spindle. If there is any deviation from this shape, cranks are likely never able to stay tight again - they develop a microscopic amount of movement and slowly ratchet off the bolt; the shape of the crank taper becomes further damaged as the bolt comes off and the ratcheting speeds up; which accelerates the damage to the crank.
Overtightening your cranks during installation will mess the taper up waaaaay faster than that, but the result is the same.
I have hear of using shim stock to revive damaged cranks, but I have yet to see it work. I am not saying it doesn't work, just that I have never seen it work.
You may be able to use locktite or something but I cannot say for sure. I have used red locktite successfully to quiet squeaky crankarm/spindle interfaces when the ratcheting action is still very minor, but not for overtightening damage.
If a crank is repeatedly retightened and ridden, damage to the BB spindle can result and may damage subsequent crank arms, so sometimes the BB spindle must be replaced too.
Edit: if you decide to try red loctite (262?), use it on the crank taper only! Do not put permanent strength loctite on your bolt threads! Use blue loctite (242?) for that.