Left crank arm fell off - replace chain set?

andyeb

Today I had the misfortune to have the left crank arm fall off, while riding back from the bike shop, following a frame warranty swap.

Seems reasonable to assume it wasn't correctly re-installed after the frame replacement.

I've heard it said of square-tapered bottom brackets, that if a crank arm is ridden loose, the whole chainset should be replaced, due to a high chance of the crank arm working loose again. And I wouldn't want that happening during a max effort sprint!

The original Shimano R565 chainset has a 24mm splined spindle, based on hollowtech2.

With these newer designs, is it OK to re-fit if a crank arm has been ridden loose, or should I bite the bullet and upgrade to a 105 chainset, to be on the safe side?

If anyone has any applicable experience in this area, I'd be very grateful to hear your thoughts.

thanks,

Andrew

crikey

Put it back on, tighten it up properly, ride.

As long as the loosening process hasn't damaged the splines and you have the end cap, it should be fine.
Don't over tighten the end cap...

andyeb

crikey wrote:

Put it back on, tighten it up properly, ride.

As long as the loosening process hasn't damaged the splines and you have the end cap, it should be fine.
Don't over tighten the end cap...

Thanks for the quick reply. Initially, I was quite concerned about damage to the splines, but having given everything a good clean, it all looks in reasonable shape to me. I guess I'll just do everything up to the specified torque (a little at a time on each side) and see if it's tight and stays tight.

The end cap/preload bolt is unfortunately MIA - wasn't able to locate it by walking back down the road. I have located and ordered a replacement online. I already have the special tool required to fit the bolt.

crikey

Again, let me stress that the end cap is only to preload the bearing and shouldn't be more than a wee touch more than finger tight. Your BB will not last as long if it is cranked down too tight.

As you say, nip each bolt up a bit at a time and all should be well.

A quick call to the bike shop to say 'Hey, my crank fell off you dozy lot, how about a new end cap?' might work well...

k-dog

Yeah, that shouldn't be a problem. Happened to me last year - somehow just worked loose. It seems to go from slightly loose to off pretty quickly so shouldn't have worn off the splines. The preload cap probably broke off anyway once the crank arms started moving. I got one for something like 2.99 so it wasn't the end of the world.

andyeb

Amazingly the shop had an end cap in stock and gave me one FOC. Now to get everything back together again.

Gutted to have missed such good riding weather over the bank holiday weekend though