"i would think that most passenges cars cannot lock the wheels at high speed (150 mph+)."
sorry, i meant to say 150 kph+.
not talking about high perf cars but the average car. so lets say we are looking at a $25k car, from 5-10 year ago (lets not discus this). take it up to top speed, 180-190 kmh probably, and hit the brakes. by the time you get 100% pressure the car is at 160 kmh and im convinced most of them cant stop the wheels/activate abs at that speed.
some other remarks:
- probably over 100 different materials are being used, up to 20 in one compound
- surprisingly most of them are cheap: glass, clay, cellulose, vermiculite, "rust", silica, carbon black, fly ash, al2o3 etc.
- sisal and coconut fibers give good results
- high perf/race pads start at $1000 (both axis), so considering the steel backing plates the compound is quite expensive stuff per wheight in the end
- mos2 and other friction modifiers go in there as well
- most exotic: banana peels
what i still cant grasp is the use of resins (epoxy, phenolic, silicone, cyanate ester) with a stability limit of 300-350°c while the pads (at least the surface, depending on conductivity) get up to 600-700°c easily.
edit: oh, "At high speed there's a lot of KE in the wheel/tire for the brake to absorb before it can lock the tire, but it'll still lock the tire once the KE is absorbed."
so what do you figure this might be in numbers? im guessing the equivalent mass of tire, wheel, nuts and disc might be 10% of vehicle mass. so deacceleratig this in e.g. 1/10 of the time will indeed double the torque neccessary. good guess?
