my cx bike has FSA gossamer cranks and since I’ve changed the bb (from the fsa one to a shimano ht2 one) I’ve noticed that the right hand crank will tap the chainstay if I pull up hard in my pedalling cadence (so mainly in lower gears). It’s already making a mark on the chainstay.
I’ve tried spacing the bb with a 2mm washer but this doesn’t leave enough meat on the axle to secure the left hand crank.

My thoughts were (considering this is a pretty rough alu hack bike)

File away a bit of the crank
or
Whack a dent into the chainstay to give some more clearance
or
Buy a new crank set with a longer axle

I’ve tried spacing the bb with a 2mm washer but this doesn’t leave enough meat on the axle to secure the left hand crank.

I’m a bit surprised as the old BB must have been slightly wider to not have presented a problem before?

I thought not all FSA cranks were compatable with HT2 ones – the axles are a different size – is the axle moving inside the BB?

Do nothing and wait for the crank to wear the clearance it needs?

Did you take the washer out of the left hand side to compensate when you spaced it? What’s the BB size? Shimano have fitting instructions on their website for the BB’s.

The FSA Cranks do fit with the HT2 bb – i think it’s the ceramic ones that don’t?

BB is 68mm and the BB Shell is 68mm – there wasn’t a LHS washer.

I like your style Nick – it’s just the tapping noise is annoying!

It doesn’t look like the BB needs a spacer on the shimano site, i think it’s a slight incompatibility / funny chainstays issue.

IME 68mm BB shell needs 2x 2.5mm spacers on the drive side and one 2.5mm spacer on the non-drive side, should give the clearance you need unless chainstays are odd…?

All I can think is that the new shimano cups sit more proud of the BB shell, reducing the overall length of axle for the crank interfaces.

With your old, narrower cups, maybe you ran spacers on the drive-side to clear the chainstay, while still leaving enough axle to fit the non drive-side crank.

If you have the old fsa cups, compare how proud they are against the shimano. You may have to source new fsa cups. Or maybe change the bearings in the old fsa cups and re-use them.

gah – old fsa cups are binned already. I think buzz is right that the cups must be slightly wider.

I’m currently feeling that some well measured hammer blows may be in order…