This is a bit of an old topic, but I feel rather than starting the same discussion all over, Ill add my 2cents here:
Disc brakes do offer more stopping power than drums according to test and our experience. Some class 7 trucks in the us (like straight trucks) have them, but manufacturers are having a hard time figuring out a good way to apply them. From what I understand there are 2 different mechanisms for moving the brake calipers using compressed air and neither are without problems. One is a threaded caliber and the other I forgot. Hydrolic application is unpractical due to the nature of the brake fluid. It may be that you could stop a truck once from highway speeds with cold brakes better, but try going down a mountain fully loaded with them!!! There is less mass in the discs to absorb heat and more importantly- less area to dissipate the heat! They would have the same contact to the rim which serves as a heat sink, but less area across the disc itself.
Also, brake shoes tend to be bigger than pads, allowing for longer life and resilience.
I dont think disc brakes are a good option on vehicles as heavy as we have them here in the US. I dont know how it is in Europe, but if im not mistakes, the weight limits are more stringent there than here and we all know what a difference 20k lbs. can make going down a 9% grade :shock:
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