How do I stop my crank bolts from coming loose?

Published by Charlie Davidson on

How do I stop my crank bolts from coming loose?

If you’ve been repeatedly riding with a loose crank arm it could be that it’s now damaged. You could try tightening with lots of torque, grease on the square taper and threadlocker (e.g. blue Loctite, but in a pinch any kind of glue works) on the threads.

What are crank bolts?

Crank bolts, as the name suggests, are used to secure the crank to the axle (spindle) of the bottom bracket(BB). While they are another of those parts that may go largely unnoticed by most riders – sometimes they are even covered by a dust cap – they may become loose and worn over time and require replacement.

How tight should crank arm bolts be?

Registered. Most square taper crank arms should be 29 ft-lbs. That is pretty darn tight. As has been mentioned, if it came loose, the crank arm is likely damaged beyond repair already and needs to be replaced.

Are crank bolts universal?

The female-threaded “outer” part has a standard external diameter of 10mm, so any crank bolt will fit into any chainset. That does not, however, mean that any set of crank bolts will work for every chainset.

How tight should crank bolts be?

Can you over tighten crank arm?

Yes, it is possible The bigger problem with over tightening a square taper is that crank arm can be deformed to the point where it will not stay tight. I always use a torque wrench when tigtening crank bolts to avoid over tightening.

What happens if you over tighten crankset?

Jobst Brandt wrote: Failure from “over-tightening” is caused by repeated re-tightening of properly installed cranks. In use, an aluminum crank squirms on its taper and, because the retaining bolt prevents it from moving off the taper, it elbows itself away from the bolt and up the taper ever so slightly…..

Why does my right crank arm bolt keep coming loose?

Anyone else’s right crank arm bolt keep coming loose? (Rail 7) Mine does every single ride now. Surprised it’s not an interference fit (the crank arm), it comes right off. It seems like a design issue, and I’m not sure how to fix it. Open to suggestions! My left crank arm bolt came undone the other day after 400-odd miles.

Why does my LHS crank bolt keep loosening?

Lost my LHS bolt during a knarly downhill & didn’t want to put the arm back on so rode out with it in my pack. Had a look this morning & the crank arm has a few knicks inside it towards the inside of the arm where it has sat halfway on moving over the steel axle.

Why does my crank wrench keep loosening up?

Dry threads have too much friction and can trip the torque wrench before the proper torque at the bolt head has been reached. Loctite performs the same function as grease in that it helps reach the proper torque. Until it sets of course. My rule of thumb is to loctite the bolts that should have it, and grease all the others.

Is there any play in the crank arm before doing the bolt up?

If yes, a small dab of thread lock might work. Is there any play in the crank arm before you do the bolt up? If yes, the arm is fubar and needs to be replaced. The play as you pedal will act like a wrench and undo the bolt.

Categories: Contributing