Bicycle Mechanics - Crank arm continually comes loose

I have a dura ace crank set and bb, fixed gear. Every few rides I have to retighten the crank arms as they work themselves loose. I have tried both loctite and a spacer neither made a difference. Is my only option to replace the bb or is there something else I could try?

Actually, and this depends on what type of crank/bb you have, you probably have to replace the cranks. If you are running a square taper set-up (which I assume you are), I would wager that the crank has started to round out and/or deformed enough that it will no longer stay on the bb. Unfortunately, when this happens, there is really nothing you can do about it. The bb spindle is steel and will not deform, whereas the cranks are aluminum, and will.

You didn't mention if it was an older square spindle, or a newer splined version (octalink?). I have overtightened a few crank bolts in my time, or perhaps they were like that when I bought them (hazard of buying used bikes). so if you're dealing with square spindle you may have actually streteched or cracked the aluminum crank around the spindle hole. If it's the newer splined type of bb/crankarm, then I don't know, I don't think you can overtighten those, as they have a definite "hit bottom" feel when you crank them down.

If it's the square type, you may have also just had it loosen once, and then the slight wobble of the crank on the spindle has altered the shape of the crank's spindle hole. IF that's the case, I'd try wiping it reallllly clean, (absolutely no grease, and then applying loctite to the spindle, and then also make sure there's no grease or oil in the threads of the bolt, or axel threads, and loctite there too. I've had fair success with this method, as I ovalized one of my cranks spindle holes, trying to get home after it loosened.

If it's cracked from overtightening, it's just time to get a new one.

You might also try JB welding it onto the bb spindle. Just make sure you NEVer want to get it off, and can get the BB out of the side with the JB welded crank arm, or you'll have to hack saw the spindle through that side.

It is dura ace's octolink setup. Does that make a difference or do you still think it is the cranks?

Pull the arm off and look at the splines down inside where it fits over the axle. Chances are that the splines are chewed up and the arm is "walking" on the axle, unscrewing the bolt (although I'm surprised this happens with Loctite). If that's the case you'll have to replace the arm — carefully, so as not to chew up the new one. I don't see how the BB could be at fault.

Btw, is there a washer under each bolt? There must be. Are you using the self-extracting bolt and ring set?


(I will refrain from commenting on the use of DA components on a fixie.)

thinking about it after the post, i put loctite on the chainring bolts, not the crank arms. i am going to go pull it apart now and take a look.

thanks for the advice.

(I will refrain from commenting on the use of DA components on a fixie.)

I have to defend the Durache' components. Mine (octalink) has lasted me 6 years so far on my commuter (which I used to deliver on). They are beat to heck and I even rode over a piece of metal that popped up into my crank/chainrings and broke through my steel frame, and the the cranks are fine aside from one of the spider arms is a little bent so my chainline waffles about 4mm each way at that point. I haven't even had to replace the chainring.

As far as the loosening of the crank, i'm now baffled, Make sure you are tightening it all the way, as i know these need to hit bottom to acheive a good grip, otherwise you can rip the splines off completeley (found that one out the hard way, so my crank is actually my 2nd crank, but i've had this one for about 6 years.) And I also can't imagine it coming loose with the self extracting bolt on there. I haven't looked at mine for a while but it seems that bolt and dust cap combo held it in place tight.

I guess I'd make extra extra sure there's no grease or oil in the threads before retrying to loctite it. The grease and/or oil will prevent the loctite from setting and/or adhering properly.

http://gallery.almostprofound.org/albums/fixed/chewed_crank.jpg

looks like it is the crank arm. the bb spines all look to be in good shape. the washer was on there and whatever bolt it came with was the one i used to install it.