Ask a Mechanic | SRAM/Shimano Road Derailleur Compatibility & Big Road Cassettes

Shimano Dura Ace 7900Welcome to our Ask a Mechanic column where our expert mechanic Daniel Slusser answers your bike maintenance questions. If you have a question for Daniel, please post it on our Facebook Wall or e-mail Daniel directly at daniel.slusser@artscyclery.com. Today’s column answers questions on cross compatibility between SRAM and Shimano road shifters and derailleurs as well as how to get big cassettes to play nice on a road bike.

Question

I have a 2011 Specialized Roubaix S-Works with stock 7900 Dura Ace running an 11-28 cassette with a compact crank and looking to getting a lower gear with an 11-32 cassette.  I’m thinking of changing out my 7900 rear derailleur for the new Sram WiFli Red rear derailleur to take advantage of the lower gear offered. Would this be compatible? If so, will the Sram Red rear derailleur work with an XT or XTR cassette, as I have WH-7850 Dura Ace wheels? I’ve heard that I can use an XTR 9-speed derailleur with my shifters. Is this correct? From:  Michael

 

Sram Red WiFli Rear Derailleur

Sram road derailleurs are not compatible with Shimano road shifters.

Answer

SRAM and Shimano 10-speed road rear derailleurs are not cross compatible. They each require dedicated shifters because the two systems each pull a unique amount of cable to execute each shift. In short, a Wi-Fli SRAM derailleur is not an option without changing your shifter too. I’ve heard of many people successfully running 11-32 cassettes with 7900 rear derailleurs, but Shimano does not officially recommend it. Whether it works or not is dependent on the length of your derailleur hanger and the position of the b-tension screw stop.
Mountain Derailleur on a Road Bike

A 9-speed mountain derailleur is an option for you to use a wide range cassette on your road bike if you have any Shimano 10-speed or 9-speed road shifters.

Any SRAM or Shimano 10-speed cassette (mountain or road) will work with your Dura Ace 7850 hub, so you have plenty of options there. You are correct that the XTR 9-speed rear derailleur is a viable option (10-speed XTR will not work) if your Dura Ace rear derailleur doesn’t play well with a 11-32 cassette. But, I think the Dura Ace derailleur should be fine.

It has been widely reported that Shimano American top dog, Wayne Stetina has been successfully running 11-32 cassettes on his personal S-Works Tarmac. I spoke to one of our top mechanics, Greg O’Keeffe (HTC Highroad team owner-Bob Stapleton’s personal bike mechanic) and he said that he has successfully set up multiple Scott Addict frames with 11-32 cassettes and Shimano Dura Ace double rear derailleurs for Bob. Since you have a Roubaix, the chances of success are even better as they come with an extra long derailleur hanger for people in your situation.
Daniel Slusser is a professional bicycle mechanic with over ten years of experience. He holds a bachelor’s degree in business administration from HSU and a master’s degree in history from Cal Poly. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.
2014-03-05T15:57:28-08:00