View Single Post
      09-18-2012, 12:05 PM   #29
Brigadier General

Drives: Jerez Black E90
Join Date: Sep 2007
Location: STL

iTrader: (3)

Originally Posted by CanAutM3 View Post
I don't believe this is entirely true. The weight from and E36 (~3200lb) to a E92 (~3600) increased by about 13% while the disc swept area increased by around 30%. This discs also have greater thickness and mass. So, IMO, the systems ability to dissipate heat has increased more than the weight of the cars.

However, is it enough to overcome the increased kinetic energy due to the higher power? Well that is another question...
Mass is a linear relationship with kinetic energy. Velocity is a squared relationship. The E90 doesn't need more brake because it's fatter, it primarily needs more brake because it's 10-20mph faster at the end of most straights than any M3 before it. So no, the M3's brakes have not increased in size sufficient to compensate for the increase in performance, let alone weight.

From an earlier post of mine:

E46 M3 at 3500lbs with driver braking from 135 mph for a 60 mph corner needs to dissipate approximately 550kcal of kinetic energy. E92 M3 braking from 145mph for the same corner needs to dissipate approximately 705kcal of kinetic energy. That's a ~7% increase in weight and speed and ~45% increase in heat load on the brakes. The E92 brakes are bigger but they aren't 45% bigger, and at bigger tracks the speed gap is even more significant. Faster cars are harder on equipment, k=mv^2. BMW had a choice to provide everything from a setup for a 150mph car with a sensitive driver to manage on track to one that can throw down qualifying laps for a whole race distance on a 100 degree day running 6" from another car's bumper. One is what we have from the factory, the other would probably need to be water cooled to fit under 18" wheels.