I have quite a bit of old freewheel gear, I was wondering whether if I build a wheel up on a freewheel hub, whether if I use an 8spd I can run 7 on it as well. I have some 7, and I think a Mountain bike on 8, parts seem a lot more available for 7. But the 8 would let me run a better freewheel for my purpose. I don't want to end up with an 8 and find if something goes wrong I am limited to the parts I can use, I would probably only run it if it was backwards compatible to the 7 stuff as well. Anyone remember?
I'm no expert, but OLN dimension for 8sp freewheels is bigger than for 7sp. Maybe you could build it for the 8sp and then use with a 7sp but this may bring problems regarding the 7 freewheel extractor.