Originally Posted by
HillRider
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.
With my FSA carbon pro compact "9 and 10 speed compatible" crankset and 9 speed chain the chain rubbed on the big ring when using the small ring with the 3-4 smallest cogs thus producing no usable overlap between rings.
I measured the spacing, found it even tighter than Campagnolo 10 speed spacing, and shimmed the small ring inward to make all the gears usable.