My crank keeps undoing itself.

So, I have a bit of a problem:

Last week on my commute home I noticed that my right pedal stroke felt a bit 'loose'. I put it down to my cleat needing tightening and looked at it when I got back. It seemed that the main crank bolt, into the BB, had started to come undone. Thinking to myself "I'm sure that's not meant to happen", I cycled it over to a friend's house. On the way there, it got a LOT looser. Dangerously so, kinda hanging and wobbling, loose. Of course, I decided to tighten it up as much as possible and hope that nothing was REALLY broken.

This morning it started coming loose again. Damn.

So, it seems that something is properly broken - what should I be checking?

I am now realising that if I'd built my own bike, I'd know how all these bits hang togeter...

see this is what you get when you buy condor! :p time to get a decent bike!

Riding a loose crank, can butcher it. If the taper square looks butchered on the crank, I would replace it, as the extra play will cause it to loosen itself. Always a good idea to tighten crank bolts, especially when new, as they tend to loosen.

You should be checking whether the bolts that go through the Cranks and into the Bottom Bracket match the BB in threading, and whether those bolts have any noticeable wear or damage to them.

That really shouldn't happen.

Was the crankset and BB bought new? I find it hard to imagine the wrong bolt is on there unless this is a pieced together conversion and someone found something that fitted well enough at the time.

I'd take the crank off using a crank extractor (Halfords sell one for about a fiver if no-one has one to lend), degrease the BB spindle and the crank area where the spindle enters, do a light re-grease back on the spindle and reassemble.

Give it a week and retighten the crank bolt if required, then (touch wood) all should be well!

Sam I'd take the crank off using a crank extractor (Halfords sell one for about a fiver if no-one has one to lend), degrease the BB spindle and the crank area where the spindle enters, do a light re-grease back on the spindle and reassemble.

Give it a week and retighten the crank bolt if required, then (touch wood) all should be well!

you should never lube a spindle!!

The second a crank feels loose you need to stop riding on it.

Going by what you say I believe you are going to have to get a new crank-arm/set.

You have had that bike for quite some time and things come loose every now and again.

If you have just had some type of crank or bb service then you could have a claim of sorts.

Some people use thread lock or locktite on threads like that. Never done it myself.

might be worth threadlocking the bolt?

Thanks for the responses guys - except you Dale :-)

So, the crank / BB were bought new with the bike, from Condor, so there shouldn't be a mismatch.

It's about one year old - not sure it should have become butchered in that time? I will ride it home very gingerly and then get a crank extractor tool and see what I can see.

Oh, and rather than have threadlock / not threadlock worries, if it is screwed I will probably be laying out for a new crank set.

How do I pronounce Sugino ? ;-)

Take the tube home, bring the extractor tomorrow.

Cheers Jon, I probably need that kind of 'safe not sorry' advice.

pronounced: soo-jhine-aaaaahh

;)

dogsballs you should never lube a spindle!!

Why? I've heard from people who say you should and people who say you shouldn't

*some *people say, if you DO grease it, you can force it further on the spindle, and deforming the inner socket of the crank arm

mashton How do I pronounce Sugino ? ;-)

Any way you like if you're paying!

xroads Riding a loose crank, can butcher it. If the taper square looks butchered on the crank, I would replace it, as the extra play will cause it to loosen itself. Always a good idea to tighten crank bolts, especially when new, as they tend to loosen.

How would it look if it were 'butchered'? Mis-shapen or mis-aligned or something?

dt interesting read!
http://forums.mtbr.com/archive/index.php/t-1930.html

dogsballs dt interesting read!
http://forums.mtbr.com/archive/index.php/t-1930.html

seams to be lots of arguments for and against

Just like anal sex really.

(No videos please, although that dogwanking yesterday had me in tears of laughter.)

Mash, the same thing happened to me. I thought that the crank had just got loose, and retightened it. From that point on, it would loosen very quickly.

Basically I had worn down the 'square' on the BB so that needed to be replaced. The crank arm is now my office paperweight...

Cheers ro-LAND, it does seem to me that I need a new crank arm.

I think a trip to my LBS is in order.

And when you do install a crank, it's one of the few bolts on a bike that you SHOULD do up WAAAAAAAAAY tight. Get a nice long-handled 8mm allen key, use the crank arm to lever against (like you're repeatedly bringing the big and little hand together on a clock from about 7.23 till they both point at the 6 ?!?).

There's a point where you think "this must be tight", but if you keep going, you'll reach the REAL tight-enough point a bit later.

How unscientific was that?

Very.

I use a torque wrench to make sure mine is done up tight enough.

All you need do is put in a long handled 8mm allen key, and then batter the end of it with the torque wrench until it will no longer move a millimetre. And then carry on banging it just a little more.