I think you may be comparing the wrong numbers here I think DC
Its the actual loss of kinetic energy that is relevent so you need to consider the absolute speeds and not just the relative difference between the starting and end speeds.
e.g. My 1.625 times more energy dissipation came from
70x70mph = 4900 units of energy
80x80mph = 6400 units of energy
50x50 = 2500 units of energy
So for the 70mph car to get to 50mph it has to lose 4900-2500 uits of energy (i.e. 2400) whereas the 80 mph car just has to lose 6400-2500 units (i.e. 3900).
3900 divided by 2400 = 1.625
I don't think the braking rate is that significant since the braking period will only be over a very short time so not much actual cooling is going to be happening here. At least if assuming max decell that the car can offer!
I think the cooling is primaily determined by the time interval taken between braking sessions and higher speed helps cool the brakes,
well at least until you brake again
I think at very very high speeds braking becomes more efficient initially because of the big air drag factor, not that apparent at normal B road speeds though.
Originally Posted by DavidCane
TB, maths a bit off I think.
70 - 50 is a 20 mph Decel
80 - 50 is a 30 mph decel.
So 20 Sq is 400. 30 sq is 900. Difference is 500, which is 1.25 time 400.
So it's gotta dissipate 1.25 times MORE energy.
As a scale, yet it's a big difference, but both those decels would not trouble most braking systems at all. Of course there's the actual decel rate to consider. You're 80-50 could take 1 second or 5 seconds depending on how hard you brake or how scared you are.
Tis best to look at energy dissipated as a result of the 'g' decel and time of the decel.