The BB30 on my roadie has been making an annoying clicking clacking noise. I’ve dismantled it and found signs of scoring and erosion to the two machined tracks on the FSA forged alloy axle that fit inside the bearing inner races:

Most people tell you that the noise from BB30s is made by movement of the bearings inside the alloy cups, which are bonded in the frame. So what is causing this scoring and surface erosion and why has a smear of bearing fit compound on the machined surfaces completely cured the noise, even 800 miles of hilly Lancashire riding later? Bear in mind that this is a relatively soft alloy forging running inside hard steel bearing races and the bearings are in good smooth-running condition. My belief is that the tiny clearance needed to allow the BB axle to slip through the inner races when dismantling is enough to allow a tiny amount of cyclical fretting and possibly even heat erosion of the machined surface.

Any thoughts?

Anyway bearing fit compound is your friend here if you have the same problem.

Yes.All the time.

mine always looks like that (only much worse). Any noise I get is always the bearings though, change those (I use cheap £2 ones from ebay that last only 12 months) and it’s fine.

C

My thoughts would be.
FSA cranks normally = mega exo bb
Mega exo bb = shit sealing
Shit sealing = ingress of water and grime
Water and grime compressed between the bearing surface and axle = pitting as shown in pic.