Shimano 8spd road/mtb compatability

[oldkit]

Hi all,

I have a set of 8 speed Sora STI's, does anyone know for sure if these will shift OK using MTB rear mechs and cassettes.

I have 8,9 and 10 speed mechs and cassettes available.

Thanks

[NUKe]

You can mix Shimano 8 speed road and MTB I think at 10 speed they start to diverge but you cant mix 10 or 9 speed sprockets with your STI owing to pitch differences.
YOU might need to fiddle a bit with the setup to get it smooth, but it will work


CJ is good with this sort of thing.

[Brucey]

8s and 9s rear mechs are interchangeable. 'Road' 10s mechs (except for 4700 series ones)will work with 8s shifters too. MTB 10s mechs won't work with 8s shifters.

Front mechs are a law unto themselves, with little interchangeability between road and MTB versions.

Obviously you need to use 8s cassettes with an 8s system, won't work otherwise.

cheers

[andrew_s]

What Brucey said: 8-speed cassette, with an 8 or 9 speed MTB rear mech.

Your existing road rear mech will almost certainly be OK up to a 30T largest rear sprocket, may or may not work on 32T (depending on your frame/gear hanger), and won't work on 34T or larger.

In general, a road shifter won't work with an MTB front mech, but it can occasionally be persuaded to work.
I spent several years using 105 and Ultegra STI with an XT front mech, which I did by clamping the cable on the wrong side of the cable clamp bolt. Setup was very fiddly, usually taking a couple of hours (no cable adjuster), but once it was working, it worked well, and didn't need touching until cable change time.
Note that it's likely that mech design has changed since, so the basic "wrong side of the clamp bolt" may no longer be appropriate, but it should still be possible to modify the leverage ratio somehow. I wouldn't recommend buying an MTB front mech in the expectation of making it work, but if you have one lying about unused, experimentation can't hurt (my XT had been used with bar end shifters).