Originally Posted by Steve_sr

I have a road bike with 10-speed Shimano that I want to add lower gearing for touring in mountainous areas. It currently has a 12-30 cassette.

I am currently thinking about changing the 12-30 road to a 11-36 MTB cassette. I will need a new RD that is compatible with a 10-speed road brifter AND will work with the 11-36 cassette. From what I can determine the RD specs required are as follows:

Largest cog = 36
Total capacity = 22 (front) + 25 (rear) = 47

From what I have read it appears that Shimano Road and MTB components were compatible/interchangeable up through 9-speed. for 10-speed I believe that the compatibility disappeared i.e. different cable pull ratios for some? components.

So will a 10-speed road brifter properly shift a 10-speed MTB RD?

I think that I read that cable pull of the 10-speed road brifter compatible with a 9-speed MTB RD? If so are there any issues with RD swing excursion or did the cog spacing change between 9-10 speed.

Thanks,
Steve