Crank unscrewing as I ride

[zimzum42]

Bit of a problem with the fixie. Left crank keeps falling off.

Kept screwing it back on tight, but gave up yesterday as had to stop every few hundred yards to screw it back.

Dismantled the whole drive train and noticed the right hand crank was a bit loose too. Could this be the problem?

Also, I have a little bit of a slack chain, might this be the cause?

The threads seem fine, and the BB seems fine too.

Any ideas?

 

[rustychisel]

not a problem with the chain... "hmm, chain's a bit slack there, Zim" but could it be the wrong BB mated with cranks. IE incorrect taper? You don't say what cranks, and what BB.

1. Even so, highly likely the installing torque was too low in the first place - most are in the order of 100 ft/lbs + a big grunt. Many many people don't power them on. If so, it's impossible to tell whether any permanent damage is the result, but that might include rounding out the [square tapers]... are they square tapers on your fixed??

2. Assuming square taper, another possibility is having Campag cranks installed on Japanese taper, they vary slightly, the result is that the cranks 'bottom out' before they really get tight enough.

Proceed with caution, maybe read a bit more on sheldonbrown.com and try to work out your precise problem. Cheers.

 

[zimzum42]

Sugino cranks on a Shimano square taper BB

I'll check for rounding off tonight, but I think it's ok

Am just pissed off I won't be able to go for a ride this evening as the bike's in bits and all my others are in the UK.......

 

[Ivan Ardon]

Loctite and a big grunt.

 

[spandex]

Loctite and a big grunt.

ER no not a good idea have a look at the posts on your over Thread

 

[fred]

bad luck. by riding your bike with a loose crank and taper BB, you've streched the soft aluminium hole in the crank. It'll no longer stay tight.

you now need to replace your cranks and have them fitted properly this time.

 

[zimzum42]

I did that, and it's all good now! Looks better too!!!!!

 

[zimzum42]

It's fukkin gone and done it again - and this time I had it fitted properly with a torque wrench.....

What's up?!?!?!?!?

 

[GrahamG]

Bin the torque wrench and bollock it up tight as you can!

 

[zimzum42]

Oh well, solved he problem, shimano BB was incompatible with the crank, so now have a new BB and everything seems OK......