Originally Posted by
Wheever
You know, I hear this all the time, as though nothing unexpected ever happens to ordinary riders; as though cars and other riders and dogs and road conditions are always predictable. Those of us who ride in traffic, especially in urban and suburban areas, can't always "plan" when we're going to have emergency brake to save our lives. It's actually not about being a pro or racer.
Thing is, disc brakes require less time and effort and hand strength to reach full effective braking force in all conditions due to the fact that the pads sit .5mm or less away from the rotors, whereas rim brake pads sit farther--usually much, much farther--away from the rims, and can take milliseconds longer to begin to "grab". (Hydraulics also respond much quicker than cables.) This may not seem like a lot, but at speed, in an emergency, those milliseconds could be the difference between a close call and death or injury. Additionally, disc brakes are much easier to modulate than rim brakes--at least hydraulics are--allowing incredible precision in applying just the right amount of braking force.
Happens, naturally, that I have a story regarding this very thing: the quicker reaction time of discs in saving my life. Bombing down a steep hill, doing something under 30mph, some ******* decided to U-turn, with no signal, right in front of me. Say less than 50'. With disc brakes, I was able to feather and hold the brakes right at the point before they locked. My tires were *literally* squealing on the pavement. I stopped so close that I had to turn my front wheel to the right so as not to hit it against the side of his car. I was close enough to reach out and pound on his roof with my fist as I yelled curses at him. ONE FOOT--That little initial millisecond it takes the rim brakes on my other bike to activate and grab--would have resulted in me hitting his car and flying over, and being very badly injured. This one experience convinced me of the complete superiority of disc brakes--between the stopping power and the fast response and ability to finely modulate the deceleration. I, personally, will never ride anything else again.
I used to set my rim brake pads a considerable distance from the rim. Upon the advice of a couple of BF posters, I tried the opposite strategy: pads set very closely to the rims. I'd estimate pads are now 1 to 1.5 mm from the rim front and back.
I have my own story as well. I was "bombing" down a moderate descent at about 35 mph. I noticed a car pulling out onto the road. I instinctively grabbed the brakes, but had to let go almost instantaneously. The instantaneous bite really shocked me. I wasn't just scrubbing speed, the brakes were biting very hard.
Fortunately, the car didn't pull into the road at all, and I continued on without any further issue, but if need be, I could have come to a stop very quickly.
Dual pivots, even cheap no-name dual pivots like mine ("axis") can bit very hard if you set the pads close to the rim. You need to run and keep your rims true, but it's totally false that dual pivots work slowly or don't bite hard.