Originally Posted by moxfyre
Yes. The spacing of Shimano and SRAM cassettes is the same for a given number of cogs, regardless of whether it's road or mountain. (E.g. all Shimano/SRAM 8-speed cassettes have same spacing, all 9-speed cassettes have same spacing, etc.)
However Campy is an exception. A Campy cassette will NOT have the same spacing as shimano etc.