Can anyone tell me if the Ultegra RD-6870 Di2 (+10-speed, 11-32 cassette) can be used with a Dura Ace 7870 Di2 system?
I don't think the 7970 RD will stretch to 32, the recommended limit is 27 from memory, although I have run 28 with no problem. I have read of people using a medium/long cage and replacing the short cage. Tbh this is beyond my technical comfort level and obviously voids any warranty.http://www.bikerumor.com/2012/10/17/hac ... erailleur/
I am just building a bike for the hills. Ended up buying a 6870 upgrade kit with the medium cage 6870 to go with 11-32 cassette.