Originally Posted by
ddscyclist
I noted three spacers in the cassette and no previous spacer...I bought the cassette 2nd hand from eBay...is there a chance this cassette could be from a non compact hub compatibility era? It's a 12-25 cassette?
Earlier non-compact freehubs will still accept a 12T small cog. It was the 11T smallest cog that wouldn't fit. As noted, most 10-speed Shimano cassettes have a 1 mm spacer behind the largest cog. It it's still on the freehub body your 9-speed won't seat properly.