Just learned BB30 bearing spacing the hard way

I was chasing a creak on a customer's Cannondale for three days until I found a tech bulletin from 2014 that said BB30 needs a 0.2mm spacer on the non-drive side for proper bearing preload. Who knew such a tiny gap could make that much noise? Has anyone else run into weird fixes from old factory docs?

3 comments

3 Comments

emma_wells8314h ago

Oh I definitely learned this one the hard way too. That 0.2mm spacer is a real gotcha. I had a similar situation with an old Cannondale Synapse where the crank would bind up after a few rides and make this terrible grinding sound. Turns out the tolerance on the frame was just a hair off and a thin spacer on the non-drive side fixed it completely. The tricky part is you can't just eyeball it, you really have to measure the gap with a feeler gauge after you torque everything down. I keep a little box of those thin shim washers in my toolbox now for exactly this reason. Once you know the trick it feels obvious, but boy does it make you feel silly the first time you figure it out.

wendy_henderson2112h ago

I read somewhere that Park Tool has a whole section in their repair guide about these tiny spacers and how they can be the culprit for all sorts of weird drivetrain noises. There's a specific video where Calvin Jones talks about chasing a phantom creak on a new build for like an hour before he realized it was a 0.1mm gap on the drive side. You'd think a thousandth of an inch wouldn't matter, but it's wild how much vibration and noise that little bit of play can cause. I've also seen people on the BikeRadar forums swear by using a feeler gauge between the crank arm and the frame to check for interference. It's one of those things where you feel like a genius when you finally figure it out, but also a total hack for missing it in the first place.

jordan_henderson1311h ago

Those little spacer gremlins pop up everywhere once you start paying attention lol. Remember when @wendy_henderson21 mentioned that Park Tool video on phantom noises - same idea applies to tightening a loose hinge on a cabinet door around the house with a single washer. It's humbling how often the tiniest piece of metal or plastic fixes something you assumed was way more broken.