Can someone fill me in regarding Shimano (and compatible) freehubs and cassettes - the normal ones; steel, not alloy, not Dura Ace etc. So;
a) Are 8,9,10 speed freehubs are basically the same?
b) So 8 & 9 speed cassettes fit straight on?
c) 10 speed need a 0.5mm spacer?
d) 11 speed won't fit?
e) 11 speed Freehubs are wider than 10 speed so that to fit a 10 speed cassette needs a 1.5mm spacer?
f) What about 8 & 9 speed cassettes with an 11 speed freehub?
a) yes
b) yes
c) sometimes, sort of (**)
d) sometimes (*)
e) sometimes (*)
f) use a spacer as required
(*) Shimano ROAD 11s uses a longer '11s freehub body'. It is 1.85mm longer than the previous 8/9/10s freehub body, so whenever you fit a cassette that is meant for an 8/9/10s freehub body to one of these hubs (with an 11s road freehub body) you have to use a 1.85mm spacer, as indicated on the EV techdoc for all shimano 'road' 11s hubs. All shimano 11s cassettes which use a bottom sprocket of 32 or smaller are 'road' type and
only fit to the longer 11s 'road' freehub body.
However shimano 11s 'MTB' cassettes use a different offset/overhang on the bottom sprocket and these fit to a standard 8/9/10s freehub body. Any shimano 11s cassette which uses a large sprocket 36T or bigger is a MTB cassette.
The complication in all this is cassettes which use a 34T large sprocket. Until recently you would expect these to be 'MTB' cassettes because shimano 'road' RDs would only accept 32T bottom sprockets. But they recently changed them so that 11s road RDs can use a 34T bottom sprocket. Currently they make two 11s cassettes (CS-HG700-11 and CS-HG800-11, both in 11-34 11s only) which are nominally part of the 105 and Ultegra groupsets respectively and these are oddball 'road' 11s cassettes because these have the shorter length to fit 8/9/10s freehubs, and indeed come with a 1.85mm spacer so that they can be fitted to the 'road' 11s freehub body.
This means if you don't want anything different to a 34T bottom cog then you can run 'road' 11s using older shimano hubs with an 8/9/10s freehub body.
(**) some shimano 10s cassettes (eg CS-6600) which use a carrier for the largest sprockets use a different offset on the bottom sprocket and come with a (0.9mm or 1.0mm) spacer. This spacer should be regarded as part of the cassette, because the cassette won't fit to any standard length freehub body without it. If you try to use a thinner (eg 0.5mm) spacer or no spacer instead, the smallest sprocket can bottom out on the end of the freehub body and the sprockets won't be properly secure: much 'biting' ensues. Cassettes without a carrier such as CS-4600-10 and CS-HG500-10 do not require a spacer and fit directly to standard 8/9/10s freehub bodies.
NB some aftermarket wheels have never had standard length freehub bodies, e.g. Mavic 10s freehub bodies were longer than the shimano standard and these often accept shimano 'road' 11s cassettes. There are probably other anomalies too.
Just when I'm getting the hang of this shimano and others are changing the freehub bodies again, mostly it seems so that you can use a 10T sprocket. Well, Mr Shimano, I didn't really feel the need for a 12T sprocket, and most of the 11T sprockets I have ever bought have ended up in the bin having served no useful purpose whatsoever. So I do not regard this as anything i could describe as 'progress'...
cheers
