Originally Posted by
Kapusta
I believe he is mistaken, and I have two working bikes using road shifters and MTB RDs to prove it.
In my experience, this is the sort of answer you get from a rep when they don't know why you are having problems.
If what he says is true, then new 9 speed mtb RDs would also not work with old 9 speed MTB shifters.
The guy at Shimano is wrong.
OP
Read this link thoroughly
https://bike.bikegremlin.com/1278/bi...compatibility/
If you have Shimano 9 speed road shifters (that are NOT Tiagra 4700) and a Shimano 9 speed mountain bike rear derailleur your problem is not incompatibility.
From the link:
"
1. Shimano
6, 7, 8 and 9 speeds
Rear shift ratio is 1.7, that is for 1 mm of cable pull/release, RD is moved left/right by 1.7 mm. Shimano calls this 2:1 ratio for marketing reasons.
All these RDs are compatible and any 6 to 9 speed RD will work perfectly with either 6, 7, 8 or 9 speed shifter. Regardless whether it’s a MTB, or road shifter, or RD. They are also compatible with Shimano 10 speed road shifters, except the Tiagra 4700 series."