I fitted a 68/113 sqaure taper BB to a recently purchased Inbred frame but the middle ring (32T) fouls on the chainstay (using as singlespeed). What size BB should I have bought?

Oh, it’s an old Truvativ Fire D chanset if that makes any difference as I’m trying to put it together out of my spares bin.
Alternative option is replace my LX HT2 BB on main bike and transfer that across HT2, but how would that be for clearance?

Thanks
Wiksey

sounds like you probably need a longer axle bb – 115 or 118mm maybe. Axle length is dependent on the crankset.

Ah, so a different crankset with that axle length could have worked but for my Truvativ one I’ll need to buy another with a longer axle.
I never could get my head round the older BBs.

Axle length is dependent on the crankset.

Not always imo. I’ve always used an axle length most appropriate for the frame…in the case of my Inbred 853, that would be 118mm regardless of chainset (Shimano & Middleburn)

The middle ring was pretty close when the crankarm was first slid onto the axle, would the extra 5mm really make that much difference? (is it an extra 2.5mm each side?

Yes…well it worked with mine.

Have you got one of the 2.5mm spacers from your HT2 BB? If so, stick that on the drive side with the square taper BB and see what difference it makes.

FWIW I tried 122mm but it just messed with the chainline too much

That’s a great idea, I’ve got a few of those spacers in the spares box.
I assume that I shouldn’t ride it with a spacer in, but just do it to check clearance?

I assume that I shouldn’t ride it with a spacer in, but just do it to check clearance?

Up to you but my UN54 bb doesn’t look like it has any threads for the closest couple of mm to the edge/lip where the shim would be so by putting a shim on, it’s not like you’ve lost much thread engagement.

The other issue is that on the non-driveside the crankarm will be closer but doubt it would foul the chainstay.

Ok, I’ll give it a go then.
The non-drive side has enough clearance to easily spin round.

Thanks for your help.

68*118 for square taper on an inbred, as you’ve discovered

I had Middleburn RS7s on a 68×113 with a 34t middle (single) ring on my Inbred. No problems (about 5mm between ring and chainstay). The chainline was roughly the same as with any HT2 chainsets I’ve had on it.