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Common sense would suggest that sudden braking is worse than gradual braking.

On the other hand, a basic physics-based analysis would seem to indicate that the two cases would cause the same wear to the brake pads. After all, if a car (or bike, etc.) travelling at speed $v$ needs to come to a stop, then the energy dissipated by the brakes is $\frac{1}{2}mv^2$ regardless of how suddenly or gradually braking was applied.

But that ignores the actual "microscopic" mechanism of how the brakes work. Could an argument be made that even though the energy is the same, sudden braking cases more wear?


Note In a real life situation sudden braking can cause wear and tear on other parts of the car, but we're only talking about brake pads here. Also, ignore the effects of wind and rolling resistance, or assume they are the same in either case

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    $\begingroup$ Common physics is an ideal model. What you need to look into is Tribology. Tribologists are the ones who are working on such problems. $\endgroup$
    – shivams
    Nov 24 '20 at 3:55
  • $\begingroup$ You may look into : en.wikipedia.org/wiki/Archard_equation $\endgroup$
    – shivams
    Nov 24 '20 at 4:57
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From the perspective of both forces and power, sudden braking causes more wear even if the energy/work is the same because everything occurs over a shorter period of time.

Higher instantaneous forces results in more stress and and higher power result in higher temperatures, therefore sudden braking causes more wear.

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  • $\begingroup$ In addition, for something like a CVT transmission or a manual transmission, the engine helps brake the car if it is given the time to do so, which reduces the wear on the brake pads. $\endgroup$ Nov 23 '20 at 23:59
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    $\begingroup$ Is there experimental evidence for this answer or is it just an educated guess? Wikipedia says "periodic, rather than continuous application of the brakes will allow them to cool between applications. Continuous light application of the brakes can be particularly destructive in both wear and adding heat to the brake system", citing this technical report. $\endgroup$
    – benrg
    Nov 24 '20 at 0:10
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    $\begingroup$ @benrg I am not interpreting "sudden braking" as repeated pulses of hard braking. I am interpreting "sudden braking" and "gradual braking" both as continuous braking actions that persists until full stop where the sudden braking is harder than the gradual braking so the car stops in a shorter period of time and over a shorter distance. If the OP intends to mean pulsing the brake, then the phrasing of the question fails to indicate that. $\endgroup$
    – DKNguyen
    Nov 24 '20 at 1:17
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    $\begingroup$ @Aqualone Yes. Consider that high temperature is generally used to form materials and how you want a material to behave when you during forming tends to be the exact opposite how you want a material to behave when you want it to be wear resistant. $\endgroup$
    – DKNguyen
    Nov 24 '20 at 1:46
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    $\begingroup$ I think we should replace "sudden" with "high-g force" to make it clear what the two different cases are. It's fundamentally the nonlinear behavior of materials under extreme stress (force, temperature) that cause this. $\endgroup$ Nov 24 '20 at 14:21
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It is difficult to ignore the physical effects because in modern systems there is disk brake system aand on pressing the brakes suddenly the car would start sliding and therefore tyre will wear down instead of breaks and in case of slowly braking the breakpads have to rub them to provide friction for the car to stop.

but if you ignore this effect completely then I suppose that the temperature increased or heat generated plays the difference in both of these processes as for instantaneous braking, temperature will increase and absorbed by the tyre and as the temperature increases rapidly the rate of absorption increases and net heat absorbed is more than that in the case of slow braking although heat evolved is same.

So increased temperature of body increases its tendency to break down intermolecular bonds as on increasing temperature activation energy decreases.

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