Loose crank arm

[Yellow Fang]

The left crank arm of my Brompton seems to keep working off. I recently had to take the crank off to remove the pedal bearing and I wonder whether I back on tightly enough. Last night I used to mallet to bash the crank on as much as I could, then used my socket set to screw the bolt in tight. However, by this afternoon, it was wobbling again. I wonder whether I need to replace the left crank now, or even worse, the bottom bracket. I had a situation like this once before and I ended up glueing the crank on with some superstrong glue that you have to mix. Surprisingly that held up quite well, but that was on a cheap bike and I wouldn't want to do that with my Brompton.

 

[dan_bo]

It'll be your crank pal. Best get it changed 'cos it'll bug you FOREVER even if you do manage to re-jig the tapers with a bit of coke can.

 

[Yellow Fang]

Bum, but I expect you're right.

 

[ColinJ]

Don't take any chances ...!

 

[Alien8]

I wouldn't bash my cranks on with a mallet!

Tightening the bolt down properly should be enough if all is well.

I would have thought that the crank is more likely to get rounded rather than the BB spindle.

 

[Zoiders]

You borkened the crank when you rode it without the bolt in properly, then smashing it with the mallet didn't help matters either.

Ruined the square taper - new crank needed.