Brake Pad Lifespan and Heat Capacity
KE per stop, rotor temp rise, wear per stop, estimated pad life by material.
Example
You enter
- Vehicle weight (lb) 4000
- Speed delta per stop (mph) 30
- Stops per mile 1
- Pad thickness (mm) 12
- Pad material ceramic
- Rotor mass (lb) 18
- Pad-set cost ($, optional) 80
You get
- KE per stop 163.14
- Rotor temp rise per stop 8.69
- Estimated pad life 8,172 mi
- Cost per 100k mi (if $/set supplied) $979.00 / 100,000 mi
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Formula or tableKE = 0.5 × m × v² per stop (J). Rotor temperature rise per stop ΔT = 0.20 × KE / (mass_rotor × 460 J/kg-K), taking one rotor as absorbing about a fifth of the stop's energy. Pad wear per stop = KE (kJ) × a per-kJ wear rate by pad chemistry; life = pad thickness / wear per stop, split front/rear by the brake bias.
Source and editionClassical kinetic-energy theorem; SAE J661 friction test, SAE J2522 (brake performance) by name; manufacturer pad-chemistry technical bulletins (Akebono, EBC, Hawk, StopTech).
Free accessSAE licensed; physical-fact derivations free in mechanics texts.
What governsEstimate. AHJ and licensed professional govern.
API field namesvehicle_weight_lb, speed_delta_mph, stops_per_mile, pad_thickness_mm, pad_material, rotor_mass_lb, pad_set_cost_usd, ke_kJ, rotor_temp_rise_C, miles_until_worn, cost_per_100k_miles_usd
- Specific heat (cast-iron rotor) 460 J/kg-K (0.11 BTU/lb-°F); one rotor takes about 20% of the stop energyengineering-practice value
- Wear rates organic 2.0e-5, semi-metallic 1.2e-5, ceramic 0.9e-5 mm per kJ (illustrative defaults; a shop-measured rate overrides)planning defaults, not a published benchmark