TugaDude

I was in an old LBS recently and found a NOS Shimano 105 SC rear derailer for cheap. Couldn't pass it up, it's beautiful.

Anyways, I have bikes that I could immediately put it on that are friction shift, I know. But I am wondering if there is a chance it could work on a 9 speed set up?

The 105 RD is a short cage and says it is for 6/7 speed SIS shifting systems. So it is for indexed systems, but what about the compatibility with a newer 9 speed set up.

The bike I'm thinking of putting it on has a 9 speed rear cassette with a 26 tooth largest ring and the front chainrings are compact double, 53/39.

Thoughts? Will narrower 9 speed chain cause issues?

Thanks all!

HillRider

It will probably work ok. I've used 8-speed designated rear derailleurs on 9-speed drivetrains and 9-speed designated rd's on 8-speed drivetrains with no problems . Since it's 105 it will probably even index properly with your 9-speed brifters. Give it a try.

well biked

No problem, it should work fine. The fact that it's designed for Shimano indexed shifters means the cable pull ratio is the same as for all Shimano road derailleurs that are designed for indexed shifting except for 8 speed and earlier Dura Ace models, which use a different cable pull ratio. In other words, your 105 derailleur uses the same cable pull ratio as a brand new 105 rear derailleur. Your proposed drivetrain shouldn't cause any problems, either.

TugaDude

Thanks for the response. It won't hurt anything to give it a shot. If it doesn't work for that bike, I'll just move it to another.