Well, I'm not exactly typical. My lowracers both have one disc in front and a caliper in back. Air resistance to help with braking is basically non-existent. Put me on a straight downhill and nothing short of a tandem team with a 70-tooth chainring can touch me. My home range is pretty flat, but I've had both lowracers in the mountains of Tennessee, with 8-12% grades and hairpins. What rotors do I use? Right now this one has a little sawtooth one that weighs 85g. The other one has just an OEM one from Avid. Unless you're running heavily loaded down big twisty hills, I think agonizing over whether Ultegra brakes better than 105 is kind of funny. But it's your money.
