Originally Posted by
LarDasse74
The spacing is not identical - it is close, but not identical. 8 speed shifters can often work adequately with a 7 speed cassette but not always. I had a bike for a while that had 7 speed indexed shifters on an 8 speed cassette (certain older shifters allow this) and it never worked to my satisfaction. Friction shifting always works.
5mm on the 7 sp and 4.8mm on the 8 sp. I agree on the effectiveness. What works better is buying an 8 sp cassette and loosing one cog. Then you'll have 7 cogs spaced at 4.8mm. You can use 8 sp barcons, available new, and just have a ghost shift.