Originally Posted by
ncscott
So is there a physical difference between a 8, 9, or 10sp crankset?
Yes but small. 9-speed cranks have the chainrings slightly closer together than 8-speed cranks to keep the narrower 9-speed chain from "skating" in the gap between the rings. That said, with some care in shifting a 9-speed chain will work well enough on an 8-speed crank.
The spacing difference between 9 and 10-speed cranks is apparently insignificant. I've used 9-speed chains on 10-speed cranks and 10-speed chains on 9-speed cranks with no difficulty either way.