Originally Posted by migrantwing

I went from 11-28 to 12-30 on a 5700 short cage derailleur. Obviously, there's a tad more needed with a 32t but with the B screw all the way in, it allows for more distance between the upper jockey wheel and the cassette teeth.

Someone on another forum gave me some great advice when I was looking at going 32t:

"Your RD will work with a 30 but the 32t will be challenging. Even with full use of B screw the issue is the clearance between the top jockey wheel and the bottom of the large sprocket. The diameter of a 28t sprocket is 113mm. The diameter of a 30t is 121mm - basically 2mm additional radius per tooth Measure what you have now and do the sums: is there 8mm spare space there ie to get a 32t in?


So, I guess the OP should measure the distance he has between the jockey wheel and cassette teeth and see if he has the required distance with the B screw all the way in. I have more than 8mm gap, so could probably get a 32t in there, I opted for a 30t in the end as I got a good deal on an Ultegra 12-30.