# Ultegra 6600 rear cog max?



## kentieb (Apr 6, 2010)

I'm new here and I've been getting confused about something. I just got a used bike with a 34/50 compact ultegra 6600 system. It came with a 12/25 ten-speed cogset. I was thinking I might like a little more range, like an 11/28. The LBS told me nothing over 27 teeth on my derailleur would do and that I'd need to go to a new 6700 derailleur to accommodate 28 teeth. I'm trying to decided between getting a 12/27 or an 11/28. Everything I've read said an 11/28 ought to work, despite what the LBS and the Shimano compatibility charts say. I know the difference between 27 teeth and 28 isn't much on the low end, but when I ride up anything more than 7 or 8% on that 25 tooth cog I start to strain and any little bit might help. Thanks so much!


----------



## frdfandc (Nov 27, 2007)

I have installed several of the 11-28 Ultegra cassettes on 5600/6600/7800 rear derailleur equipped bikes. The 6600 rear derailleur will accommodate the 11-28 with out a problem. Will need to make a B-screw adjustment.


----------

