Brake Pedal Ratio and Line Pressure

Master-cylinder force = pedal x ratio x booster; line pressure = Master-cylinder force / (pi/4 x bore^2); clamp = line pressure x caliper area; brake torque = clamp x 2 x friction x rotor radius. A 50 lb pedal at 5:1 manual through a 7/8 in master makes 416 psi -> 1,663 lb clamp -> 5,987 in-lb per corner; swap to a 1.75 in master (double the bore) and the pressure drops to 104 psi, exactly a quarter, for the same leg -- the whole manual-vs-boosted trade. The 2 in the torque is both pad faces. A design aid; the pad friction, thermal state, and system compliance govern.

mc_force = pedal_force x ratio x booster; line_pressure = mc_force / (pi/4 x bore^2); clamp = line_pressure x caliper_area; brake_torque = clamp x 2 x friction x rotor_radius.

Hydraulic brake force chain (Pascal's law; SAE brake-system design practice), first-principles, by name; the actual pad friction, thermal state, and system compliance govern.

The hydraulic brake force chain is first-principles Pascal's law; the pedal ratio, bore, caliper area, and rotor radius come from the vehicle's brake components.

Estimate. AHJ and licensed professional govern.

Field names used by the API: pedal_force_lb, pedal_ratio, booster_factor, mc_bore_in, caliper_area_in2, pad_friction, rotor_radius_in, line_psi, clamp_lb, brake_torque_inlb

• Bore squared line pressure ~ 1/bore^2, so doubling the master-cylinder bore quarters the pressurePascal's law
• Two pad faces brake torque includes a factor of 2 for both pad faces clamping the rotorcaliper geometry
• Idealized ignores thermal fade and system compliance; the pad friction and thermal state governscope of this tile