Originally Posted by
Atlas Shrugged
Just another long, disproven, urban myth from decades gone by.
In fact, pumping your brakes (repeatedly applying and releasing them) is generally less effective and potentially more dangerous for managing heat than proper technique.
The physics of braking is essentially the conversion of kinetic energy (motion) into thermal energy (heat) through friction. To slow a vehicle by a certain amount, a specific amount of heat must be generated. Pumping the brakes doesn't change the amount of heat required; it just changes the timing of when that heat is generated.
You are misunderstanding what I said. I do not advocate pumping brakes in a car on a downhill. I would not do that nor should anyone else. A car has engine compression to run against on a downhill and that is far more efficient way to slow a car without using the brakes than dragging the brakes all the way down a hill.
I do, however, advocate “pulse braking” on a bicycle. A bicycle does not have engine compression and relies almost entirely on the brakes to slow the bicycle. There is some wind resistance at higher speeds but the brakes do the vast majority of the work. Dragging brakes on a downhill on a bicycle will lead to far more heating of the rims or rotors than a car because the heat goes into the tire and rim or the rotors and calipers which are pretty good heat sinks but poor heat exchangers. “Pulsing” the brakes on a long downhill allows for the heat that has accumulated to radiate away from the braking surfaces without adding heat that steady application would.
Why Pumping Isn't Better for Temperature
- Reduced Cooling Time: While it seems like the "off" phase of pumping allows the brakes to cool, the intervals are usually too short for significant heat dissipation. High-performance braking systems require consistent airflow over time to shed degrees.
- Peak Heat Spikes: Pumping often leads to more aggressive stabs at the pedal to maintain control, creating "flash" temperatures that are higher than the steady heat generated by constant, light pressure.
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This might be true for cars but not for bikes. Bicycles have a much lower tech/performance braking system. A bicycle also has less heat to build up and less to dissipate than a car by at least an order of magnitude. We don’t go as fast as them nor have a much mass to stop.
Additionally, unless the car (or bicycle) is stopped, air is always flowing over the brakes. Even if you pump the brakes in a car…again, not something I would advocate…the car isn’t stopped so the air flows constantly over the brakes surface.