Wobbly crank arm

[bigandclever]

This morning was pedalling along quite happily until I noticed the left crank started wobbling from side to side as I pedalled. So I stopped, tightened the bolt with a multitool (probably had about 7 or 8 complete turns to do, did it up as tight as I could), and started off again. Then I got maybe 3 revolutions and it's loose again, and gets progressively looser the further I ride.

Have I (a) busted something that needs replacing or (b) worn something out that needs replacing or (c) am I not tightening the bolt enough (or even over tightening)?

[neil_cardiff]

You need a new one.

The tapers on the crank wear if ridden loose, and so if you tighten it up again, it'll only loosen again pretty much straight away. Nowt you can do

Common problem, now allieviated by the new designs of crank/bb interface these days that are much more reliable.

Edited by neil_cardiff on Monday 4th September 11:49

[bigandclever]

Cheers Neil, got a new arm put on tonight. By the time I did the 6 miles or so to the bike shop this evening, the square hole was very much a round one

[beyond rational]

Use threadlock on the crank bolts, ISIS or whatever will still come loose

[m12_nathan]

I had the same, bought a Shimano Hone Crank - problem solved as there is no taper to break, the external bearings are massive and the actual crank is thicker too. No flexing at all.