Originally Posted by
karldub
Hi,
I have a 80-90's Concorde race frame with a vintage Dura Ace Crankset. The other day, my crank arm started to unscrew itself from the BB and ultimately came off completely. The crank arm has a crack in the arm which might be causing it to unscrew. However, I'm not sure the BB is broken or if it's supposed to look like this. It looks like one part of the bolt, the "thread stem" is merged/a part of the bottom bracket and then theres just a small nut to screw back.
I have tried to screw the crank arm back with help of the nut, but after a couple of miles it goes back to keeps unscrewing itself.
Is this bottom bracket also broken or is this some niche type of crank set? Or can I extract the "threaded" stick that comes out of the BB, or is this an integrated part of the BB?
You can remove all of the bottom bracket to degrease and repack. You can check for cracks, but a picture of the crank arm might help.
Its an older Bb axle, where the attachment is male, rather than the female of most modern BBs. It is likely that either it was not torqued enough and the taper hole expanded or the crack makes proper torque impossible.
hope that helped!
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