BB30 crank move rightward and then stays there

Equipment
1

I went for a ride yesterday and became frustrated with a number of dropped chains when moving from big to small chainring. The BB30 bearings were replaced a couple of months ago. At most the bike has seen a few hundred miles. I just took a look at the bike and noticed that the whole crankset had shifted right about 1mm, compressing the wavy washer. I tapped the crank with a mallet and it went back into the correct position.

I’m going to continue riding the bike and keep an eye on this issue but has anyone seen and resolved this problem?

2

Looks like whoever replaced the bearings missed a spacer when they put it back together. Probably on the NDS, but could be either.

-Tim

3

I find the correct number of spacers to be a bit of a mystery. The spacers are clear plastic. I know when I purchased the bike it had at least one, maybe two. I’ve long forgotten which side they might go on. I guess it wouldn’t hurt to install one or two on the non drive side.

FWIW its a CAAD10

4

The number of spacers is crank specific. If SRAM, then you can adjust the preload pretty easily. I don’t know about shimano

5

The number of spacers is very bike specific. I’ve had one with 1, and a friend had one with 3. Both cannondale road bikes, both SRAM cranks.

If after torquing the crank bolt properly, the crank spins freely, and has no side play, you’re good. If you add spacers, check that the crank spins freely as you tighten the bolt in small steps. You don’t want to damage the bearings by over-compressing them.

-Tim

1 Like
6

I installed 3 spacers - much improved but I’d still drop a chain about once a ride. A big improvement was that I could just shift to the large chainring to restore the chain. Then I went to 5 spacers and now the wavy washer looks over compressed and I still dropped the chain. I’m thinking about going back to 3.

The chainring is only 6 months old and should be in good condition. Either I could try a chain catcher OR I could install another crank. I have a BB30 → GXP bottom bracket and a GXP crank I could install although I’d prefer to save that project for winter. The chain does seem to float back and forth between the front deraileur as I turn the crank. Alternatively I could switch to a shimano crank - I’m pretty sure their main innovation is front shifting is to make beefy chainrings to limit the potential for deflection.