My brother in law brags how he gets 100k miles between changing his brake pads. Modern brake pads generally last about 50k miles. This is a remarkable feat but what does he do different? Brakes of course slow down the forward kinetic energy of the car. To reduce speed the kinetic energy of forward motion has to be converted to heat by the friction of the pads and rotors. The formula for kinetic energy is E=mass x velocity squared. Lets consider this. To slow down from 90 mph to 60 mph, assuming mass is 1(car) the kinetic energy change is the difference between 90 squared and 60 squared or 8100 – 3600 = 4500 energy units (EU) of heat. So if is one is driving at 90mph and pushes the brakes to slow down to 60 mph, the brakes wear down or heat up 4500 EU.

Now if you are driving at 30mph on a city street and apply the brakes to stop, Then you are dissipating 30 squared or 900 EU to reach 0 speed. Therefore slowing down from 90 mph to 60mph is 6 times as wearing on the brakes as one time stopping from 30 mph.

Lets consider a more modest highway speed change. Lets analyse slowing from 60 mph to 50 mph. By the same method this is the difference between 3600 EU and 2500 EU or 1100 EU. Of note, slowing from 60 mph to 50 mph is more wearing on the brakes than going from 30 mph to a stop (900 EU).

Going back to my brother in law, he must never touch the brakes when moving more than 30 mph.

John J Klosak