Andrew_P
In between here and there
Well my 2010 Roubaix comp came with 28-11 compact and cleared 5000 miles without any problem.. In fact the chain length was too short for 5700 rear mech so had to put a longer one on. Running 25-11 now.the 5600 rear mech will not take 28T max sprocket size. The Shimano website says 27T max and I use a 27T with mine and I agree that it's right on the limit (i.e. it doesn't run very smooth but is ok). Only the 5700 rear mech can handle 28T. Many of the 5700 components are not compatible with 5600 ones, or at least according to Shimano. That's why it seems odd to go for 5600 when they are already difficult to find. 5700 would make more sense, even if the components are no better.