haagar

You can wiggle the chain side crank with your hand on my single speed (towards and away from the frame). The bolt is tight and when you take off the crank, you can see that there is some wear. More wear than would occur from installing or removing the crank.

Is this something that I should be worried about?

Bikewer

Yes, you should. There should be no movement whatever. What sort of crank is it? One of the older square-taper jobs, or one of the newer hollow-billet numbers?

DMF 

If, as you say, the bolt is tight, it means that the bolt has bottomed and either the bolt is the wrong length or the crank arm is ruined. Take the crank arm off and run the bolt down all the way. If the head contacts the spindle, replace the crank arm.

Don't keep riding it like that. You are placing unusual stress on the bolt head and will eventually break it off.

filtersweep

Is it the crank or the BB that is loose? Either way, you should repair it.

s1nglespeed

If it's a square tapered spindle, and you can see wear in the spindle hole of the crank, the cranks are done for. You don't create wear in that socket by mounting or removing the cranks. Wear is created in that area by pedaling on loose cranks. I did that myself last week and just ordered a new set. There was almost no rounding noticeable inside the crank sockets, but I couldn't get them to stay on for more than a few miles, even with considerably more force on the mounting bolt than the recommended torque.

haagar

Thanks for the tips. It is an IRO square taper crank. I took the crank off again and tried threading the bolt all the way in. It went all the way in, but there were a couple of rough spots. After I put everything back together again, the play is gone. I will keep a close eye on it.

Bill Kapaun

Ride it a couple minutes and recheck the bolt tightness. If tight, repeat at longer intervals until you are confident everything is "kosher".

s1nglespeed

Re-tightening the bolts might be worth trying (to my mind, as a very last resort), but Jobst Brandt's article cautions against it:
https://www.sheldonbrown.com/brandt/i...ng-cranks.html

DMF 

Interesting article, thanks.

But it begs a question. If the crank loosens up and one is not supposed to retighten, what is one supposed to do? Immediately replace the (probably new) crank?

Quijibo187

correct.

DMF 

That's a strong argument for getting the bolt torque right in the first place.

s1nglespeed

I can tell you that the only time I have had a crank come loose during a ride, I was never able to get a good fit again. I started carrying the big allen wrench with me on rides. Got to the point where I just finally replaced the spindle and the cranks. And it was all my fault ... I had been re-packing my BB bearings and didn't re-install the cranks with the proper torque.

Quijibo187

also correct.

tellyho

Cranks need to be torqued on like a mo-fo. Haul on that wrench and pray. Then replace your BB and crankset - scary to ride around on a crank that could fail.

ChillGrean

Resurrecting this thread and this very knowledgeable (if poorly written) article on crank failure.

Is the author saying that you should avoid uninstalling and re-installing properly set cranks? I like to take mine apart at the end of the season for cleaning, and then re-install in the spring. Is this a bad thing to do?

dscheidt

No. One of the problems with tapers is that they tend to wiggle a bit. With a square taper crank, there's a bolt or nut that keeps it from wiggling off. But they can wiggle on tighter. when that happens, the bolt or nut loses preload, and it appears loose. So someone comes along and tightens the bolt, forcing the crank further up the taper, and damaging the crank. Correct course of action when encountering a loose bolt is to pull the crank, inspect it, the spindle, and the bolt, clean, properly lubricate things, and reinstall the crank to the correct torque. In practice, I don't think this is usually a problem, as the spindle bolts aren't often inspected unless there's a reason to take it apart.

ChillGrean

Much clearer explanation. Thanks!