Fergp

I am replacing the standard rear derailleur cage on my DI2 6770 with a longer cage from an 6700 GS derailleur so I can run a bigger cassette. It seemed pretty straight forward, however when I tighten the main pivot bolt with the long cage installed on the 6770 it is extremely tight. It feels good if I back it off slightly but then I'm sure it will quickly loosen up. What am I missing?

Thanks, Paul

well biked

Both the 6770 Di2 derailleur and the 6700 GS show a largest cog spec of 28t.

hueyhoolihan

they are probably not designed to be interchangeable. if you've read it in Shimano docs that they are, i believe you and it's probably something else.

BTW, i may be wrong here, but i've been led to believe that cage length is not a factor in determining the largest cog limit.

well biked

The cage length does not make the derailleur compatible with a cassette with a larger cog. A short cage 6700 derailleur would be just as likely to work okay with a 32t cog as a GS 6700 RD, the largest cog compatibility is a derailleur body angle issue and is also affected by the geometry of the derailleur hanger's proximity to the rear axle.. I've never swapped parts on a Di2 RD, however, but the longer cage by itself isn't going to make the Di2 RD work with a larger cog.