Originally Posted by
cyccommute
If you are using Shimano IG or SRAM 8 speed, the thickness of the cogs are close enough (1.85mm for the cog and 3.15mm for the spacer for 7 speed vs 1.8mm and 3.0mm for 8 speed) that they can work.
Did you mean to say Shimano IG (Interactive Glide)? I think the sprocket thickness on those is pretty thick (with thin spacers). I think it's Shimano HG (Hyper Glide) that's compatible with SRAM, right?
https://sheldonbrown.com/cribsheet-spacing.html
(Having said that, I think IG's sprocket spacing itself...center-to-center...is compatible, so should work similarly as long as the chain will support it.)