Rear Mech Capacities

dru

Hi People,

I've got a couple of questions regarding suitability of rear mechs and cassette options:

I've got a FSA/SRAM red build with compact 50/34 front with a SRAM Red rear mech, with a 12/25 cassette.

This is 27 tooth difference. Does anyone know if I can go to a 27 or 28T rear cassette without issue?

Also the same goes for another build I'm doing, which is FSA/Shimano Ulterga rear mech. The rear mech is a short cage.
Its a race double (53/39) and looking at what cassette options I could run. Would an 11-28 cassette be acceptable?

Cheers,

Dru.

markos1963

Yes,Sram does a 11-28 cassette for the road so it should work with either the Sram or the Ultegra rear mech'. You might have to 'fiddle' with the B screw to get it to clear the biggest sprocket but it usually works fine. Just be careful with the chain lengths.

sungod

the red rear mech capacity is 33t and it's rated to work with up to a 28t largest sprocket

ultegra short cage specification depends on generation...

6700 is rated 33t capacity 28t largest
6600 is rated 29t and 27t
6500 is rated 29t ans 28t

chances are the 6600 will be ok, they are conservative specs

and as markos1963 says, adjust it and make sure chain length is spot on