Disc's are more conducive/effective for ABS modulation ( ie faster), and IMO, why they are being phased into big rigs.
If you are fading rear brakes on the street in a car, you are driving seriously way over your talent level.
Big trucks/buses have larger rear brakes because the rears are often dual tires (larger contact patch), and have the higher weight percentage, and on long WB's relative to COG height, the weight transfer is much less.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
