If all you're replacing are the front and rear derailleurs, you'll be fine. Worse case scenario is you'll get a bit more chain rub on the (very slightly) narrower FD cage. If so, next time you replace your chain, go with a 10 spd.wphamren said:I see lots of info on compatibility of 6700 with 6600, but I'd like to stick with 9. So, can I upgrade the derailleurs to 6700 and keep the cranks, chain and cogs 6500? I believe that my derailleurs are about "tweaked" out and need replacement. thanks.