MTB Derailleur compatibility

[Tony]

My understanding is that any 7, 8, or 9 speed rear mtb derailleur will work with Shimano road 10 speed shifters. And, any Shimano mtb or road cassette will work with this setup, is this correct?

[andrewsuzuki]

My understanding is that any 7, 8, or 9 speed rear mtb derailleur will work with Shimano road 10 speed shifters. And, any Shimano mtb or road cassette will work with this setup, is this correct?

As far as ratios go, yes it'll work.

There's one caveat which is pulley play. 7/8/9-speed derailleur pulleys have more lateral play than 10/11-speed pulleys by design. Since 10-speed road tolerances are tighter than anything else, this can introduce some issues with the chain not wanting to shift (esp. going to the next larger cog). The solution is to just get a pair of 10/11-speed pulley wheels.

[dddd]

My understanding is that any 7, 8, or 9 speed rear mtb derailleur will work with Shimano road 10 speed shifters. And, any Shimano mtb or road cassette will work with this setup, is this correct?

The other issue is that 7s derailers typically lose their indexing accuracy going up to the largest cog of any cassette with more than 7 cogs. The symptom is that of the cable tension not quite being adequate, but when tension is increased to run quietly on the largest cog, shifting to the smaller cogs becomes hesitant.
And no, this was not a cable-friction or limit-screw issue in the multiple instances I observed (and corrected, with an 8s derailer).
When Shimano's derailers went to 8 speeds, they carried the designation "Integrated8 SIS". This was not just marketing, as might be assumed.

[oldpotatoe]

My understanding is that any 7, 8, or 9 speed rear mtb derailleur will work with Shimano road 10 speed shifters. And, any Shimano mtb or road cassette will work with this setup, is this correct?

Correct altho you'll get the best performance out of 8s/9s rear ders.

BUT this is a '7s' rear der and if in good shape, will work fine.

[commonguy001]

As far as ratios go, yes it'll work.

There's one caveat which is pulley play. 7/8/9-speed derailleur pulleys have more lateral play than 10/11-speed pulleys by design. Since 10-speed road tolerances are tighter than anything else, this can introduce some issues with the chain not wanting to shift (esp. going to the next larger cog). The solution is to just get a pair of 10/11-speed pulley wheels.

This is not only interesting but my experience exactly. The fix makes sense and i need to do this with my wife’s bike we’re running a long cage 9 speed Deore on with 7800 10 speed shifting.

[oldpotatoe]

As far as ratios go, yes it'll work.

There's one caveat which is pulley play. 7/8/9-speed derailleur pulleys have more lateral play than 10/11-speed pulleys by design. Since 10-speed road tolerances are tighter than anything else, this can introduce some issues with the chain not wanting to shift (esp. going to the next larger cog). The solution is to just get a pair of 10/11-speed pulley wheels.

BUT probably 10tooth pulleys. Not sure an 11t(11s rear ders) pulley would fit.

Good option.