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I'm about to buy a new bike fitted with a Deore 3x10 groupset. I want to replace that with a spare SLX 2x9 groupset I have. Don't want debate whether that's an upgrade or downgrade, point is it works for me as I'll then have compatibility across all three of my bikes.
Anyway, only thing I don't know is whether I can just put a 9 speed cassette on the hub. Cassette is a SRAM PG990, and the hub is a generic Giant one, if that makes any difference. Guy in the LBS said it'd work but I'd need a spacer behind the 9 speed cassette as its narrower, but I'm a bit dubious about that!
yes, IIRC 8, 9 and 10 use the same freehub width (so the sprockets are closer together).
Guy in the LBS said it'd work but I'd need a spacer behind the 9 speed cassette as its narrower, but I'm a bit dubious about that!
you are right to be as it's bollox.
Shimano 10 speed road cassettes used to need a 1mm spacer because they where narrower than the 9 speed, not sure if this is still the case.
So there's no such thing as a ten speed freehub versus a nine speed one - I just slide the ten speed cassette off the freehub and fit the nine speed in its place? PS: Only talking MTB here, not road.
Hmm. I have had a rear wheel before - Ritchey WCS road wheel, that would not allow an 8 speed cassette to fit, but an 9 speed would.
Certainly no difference in Shimano 9sp / 10sp cassettes, I've gone from 9 to 10 without any issues.
+1 footflaps
Great, thanks!
I had an issue once with a 9 SPD cassette needing a spacer. I didn't have one, but a bb spacer was exactly the right size, so fitted that and it worked perfectly!
So you shouldn't need a spacer, but if you do it isn't a problem.