Originally Posted by
Rolla
If disc brakes are useful on all those other bikes, I would think they'd be useful on a road bike, where the speeds are higher. But I've never ridden a road bike with disc brakes, as you presumably have.
Back in 2018 or 19 I actually tested my Lynskey road bike with rim brakes against a guy who bought a brand new bike with hydro disk brakes to see who would stop the fastest. I had 23mm tire on the front and 25 on the rear Vittoria Rubino tires, he had Conti 4000s 25 mm tires all round; I had Shimano 105 rim brakes, my pads were Kool Stop Salmon, and he had DA Hydro disks with factory pads; the total weight of our bikes and body weights were within 5 pounds of each other; we inflated our tires according a tire calculator for a our size of tires and weight; the only rule we had was that we had to stay on our seat and not slide our butts off the back of the saddle to put more weight on the rear this way there was no ability of one person being able to slide further off the rear than the other person could. The test was going to be 3 sets of 3 runs, 1st run was at 15 mph, the 2nd at 20, and the third at 25. The results were interesting, on the first 2 sets we stopped within a foot of each other, sometimes I stopped a tad faster and sometimes he did, that was probably due to reaction time variance; the last set got interesting, the first stop I stopped about a foot and half faster, not a big deal but the second stop I stopped about 3 feet faster, and the last stop I was nearly 7 feet shorter. What happened we asked ourselves? so he touched his front disk rotor and singed his finger and left a whitish burn mark, but didn't singe his finger when he touched my rim though it was hot. What we determined was that the smaller rotor could not dissipate the heat as fast as the much larger rim could and thus he suffered brake fade. The reality is that all a rim represents is a disk, thus rim brakes are actually disk brakes, but the size of rim allows for more surface cooling and thus less chances for brake fade.
Supposedly the problem with using rim brakes on a touring bike is that you can wear out the rim pretty fast, but people have been touring all over the world for over 100 years on rim brakes and they didn't have a lot of issues with rim failures, so not sure if there is a huge advantage there, but if you run into mud disk brakes are more advantageous.