Originally Posted by
jimc101
The RD may work, but may not. For the STI's these won't work for 2 reason, 5500 (the last 9 speed 105) is 9 speed, and won't have enough clicks to shift a 10 speed cassette, and the ratio on the brakes pull has changed, they will still work, but using older and current Shimano STI's/brake calipers together gives less than optimal performance.
Totally false.
I have 2 bikes setup with 5700 and 6700 shifters and derailleurs respectively, both with 5500 brakes. The "less than optimal" argument is BF fluff from back when Shimano said the pull ratio was different. There is no mushiness or any other "problems."