Shimano drivetrain compatibility 9spd vs 10spd r-ders

[Louis]

I read somewhere that if one has say, an Ultegra 9spd setup and for some reason needs to replace the rear dérailleur only, a 10spd will r-der will work just fine.

Here's the question: Is the same true for MTB rear dérailleurs? Can a new 10spd r-der replace a 9spd?

I know that for 9-spd all r-ders, "road" or "mtb" are interchangeable as far as the indexing goes. I don't know if the same is true for the new road and MTB 10spd. If so, then I would expect the 9spd mtb to be interchangeable with the 10spd mtb. (Except for the lack of barrel adjuster on the "Shadow" models. Hopefully not all the 10-spd r-ders are made that way - that's one thing I have not yet checked.)

TIA

Louis

[rice rocket]

10 spd Dyna-sys Shimano has different geometry than the rest of Shimano's stuff.

[sg8357]

10 spd Dyna-sys Shimano has different geometry than the rest of Shimano's stuff.

Which means use a 9sp mountain derailer on your 10sp road bike,
when doing a Sram Apex style setup.

[oldpotatoe]

I read somewhere that if one has say, an Ultegra 9spd setup and for some reason needs to replace the rear dérailleur only, a 10spd will r-der will work just fine.

Here's the question: Is the same true for MTB rear dérailleurs? Can a new 10spd r-der replace a 9spd?

I know that for 9-spd all r-ders, "road" or "mtb" are interchangeable as far as the indexing goes. I don't know if the same is true for the new road and MTB 10spd. If so, then I would expect the 9spd mtb to be interchangeable with the 10spd mtb. (Except for the lack of barrel adjuster on the "Shadow" models. Hopefully not all the 10-spd r-ders are made that way - that's one thing I have not yet checked.)

TIA

Louis

No(thanks shimano). The new shimano 10s MTB rear ders are compatible with ONLY shimano 10s shifters. But if ya got a 10s road STI, just use a shimano 9s rear der or any road rder...just not a 10s shimano MTB rear der.

Similar but different for sram. Their 10s MTB rear ders ARE compatible with their road shifters but their 9s MTB rear ders are not..confusing isn't it.