Crank Bolt Loosening

Afternoon all,

The other night I was out riding, having just learnt to skid, finally.

After about an hour or so I noticed my cranks were extremely loose, and when I got in it was the crank bolt.

I figured since it never happened before until skidding, so tested it out right after tightening it up, few skids and it was loosened again slightly when I checked it.

Anyone else had this, is it common ? Solutions !?

Cheers !

T

Once you have ridden on a square taper crank that is not perfectly tight, the taper will be damaged and it is very hard to get them to stay on. You can tighten the bolts as hard as you can and it will still loosen off.

Some people have had luck with filing the taper down, others have used shims made from alloy can.

Oh dear. New BB and cranks otherwise?

grease the thread of the bolt and the faces of the tapers (cranks and spindle) you will get them on much tighter without damaging them.

although, as said above, if you've damaged the tapers of the cranks by riding on them when loose, you could be in a little trouble

BB should be fine, the spindle is very hard and difficult to damage, the cranks are much softer and go first

Oic.

It was the left-hand crank... right?

Try locktite aswell - nothing to lose (loose).

blergh......locktite. Not necessary IMO grease FTW.

but if the crank is already shagged + it won't stay on....?

Both were loose... left hand only a little, right hand much moreso.

Cheers for all replies so far, hopefully it hasn't done too much damage then...

bit too desperate, once you've got to that point it's not going to help. It'd be much better to buy a £30 set of cheap cranks than risk a dangerous failure mid spin.

new crank time, in my experience.

bit too desperate, once you've got to that point it's not going to help. It'd be much better to buy a £30 set of cheap cranks than risk a dangerous failure mid spin.

Fair point - lets hope the OP hasn't made an expensive mistake...

So you think the BB will be ok ? Any way of telling ?

I have some more cranks, just really like this one, oh well...

Torque Fail + Riding on Loose Cranks Fail = Total Crankset Fail.

I'd put money on it, takes a lot to damage a BB spindle. What type is it? cartridge or cup and cone? I've heard tell of axles getting bent slightly but that wouldn't make the cranks come loose so I severely doubt it's that 99% sure that the square on your cranks has rounded out slightly.

take them off, clean then and the BB, grease the axle and the crank bolt threads, re-fit and ride for a bit (not too fast but enough to test). If they come loose again, get new cranks.

what is your crank and bb combo? perhaps you're mixing JIS and ISO and so the cranks aren't sitting very tight on the spindle.

mixing ISO and JIS won't cause that, it'll only put the chainline out slightly.

Cheers very much Stevo, I'll do as you suggested and see what happens! Hopefully it's not too bad, I can live with having to get new cranks I guess!

where are you based? i can have a look if you like? no worries if you want to sort it yourself

I'm right up North mate, and guessing you're in London?

aye, and South London too. Good Luck! Keep us posted

.......am I missing something, what is the point of skidding? teaching yoursef bike control in a 35mph criterium is so much more satisfying

I don't have a track outside my front door.

what is your crank and bb combo? perhaps you're mixing JIS and ISO and so the cranks aren't sitting very tight on the spindle.

so a campy record bb should marry up fine to a pair of old shimano 600 cranks ?
jis vs iso