I've got a BSA BB (24mm axle), and need to put a drive side spacer in as I've got some strange rubbing noises. Do I put something on the thread side or the crank side of the bearing?
What crank? Modern cranks (Hollowtech ii etc.) won't tighten properly if you put in more spacers than they were designed for.
Did you measure the BB width? Can you find where the rubbing is coming from?
Both will work, provided there's still enough clamping force to hold the two parts of the cranks together, but given the choice I'd go for a spacer between the BB shell and the DS BB bearing.
I've got a BSA BB (24mm axle), and need to put a drive side spacer in as I've got some strange rubbing noises. Do I put something on the thread side or the crank side of the bearing?