Automotive Brake Calculator

 


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Pedal ratio is calculated by dividing the distance from "Leg Line of Action" (L.L.A.) through the center of pedal pad to center of pedal pivot, by the distance of center of pedal pivot to "Push rod Line of Action" (P.L.A.).

L.L.A. = a straight line through the drivers hip joint and the pedal pad.
P.L.A. = a straight line through the M/C push rod.

The sketch below shows three different designs. The first one is used on street cars and race cars. The second and third only on race cars. To keep the drawings simple, a booster between push rod and master cylinder is left out.

Pedal ratios for brake systems without a booster usually vary between 5 : 1 and 7 : 1. For brake systems with a booster, this ratio usually falls in the 2½ : 1 to 3½ : 1 range.

Other ways to calculate Pedal Ratio (A/B):
- Measure the distance of travel for pedal pad (A) and master cylinder push rod (B).
- Measure the force on both pedal pad (A) and master cylinder push rod (B).

Whichever method you use, always keep in mind the right lines of action!

Brake Pedal Ratio

 

Last Update: 03/30/2017
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