Engine Tuning and Chassis
Brake Pedal Ratio Calculator
Calculate pedal mechanical ratio and ideal pushrod force. Geometry changes through pedal travel and friction reduces ideal force.
Values used in the formula
Enter current information for Brake Pedal Ratio and leave unrelated adjustments outside the form.
Scope of the estimate
Calculate pedal mechanical ratio and ideal pushrod force — use the equation to compare setups while keeping the test conditions explicit.
Geometry changes through pedal travel and friction reduces ideal force — that condition defines when pedal ratio is comparable with another result.
Traction, grade, wind, temperature, driver input, and control-system intervention remain outside this simplified model — for pivot-to-pedal distance, the page specifically expects distance from pedal pivot to driver force application.
Formula used on this page
In “pedal ratio = pivot-to-pad length ÷ pivot-to-pushrod length,” the equation links pivot-to-pedal distance, pivot-to-pushrod distance, and driver pedal force to pedal ratio.
No term beyond pivot-to-pedal distance, pivot-to-pushrod distance, and driver pedal force is introduced in “pedal ratio = pivot-to-pad length ÷ pivot-to-pushrod length.”
Collecting compatible values
Document Pivot-to-pedal distance as distance from pedal pivot to driver force application — this means you should measure from the stated reference points and note whether the vehicle or component is loaded.
Pivot-to-pushrod distance. Distance from pedal pivot to master-cylinder pushrod — for this measurement, measure from the stated reference points and note whether the vehicle or component is loaded.
Driver pedal force: Applied force at the pedal pad — a compatible entry should use a measurement or specification from the exact component and operating condition being evaluated.
Example using the displayed inputs
The sample vehicle case enters Pivot-to-pedal distance = 12 in, Pivot-to-pushrod distance = 2.4 in, and Driver pedal force = 80 lb.
That specific combination leads to Pedal ratio = 5.00:1.
A related vehicle record may need to estimate ideal brake line pressure from pedal force and system leverage, a relationship covered by the Brake Hydraulic Line Pressure.
Interpreting the headline value
Pedal ratio answers “Calculate pedal mechanical ratio and ideal pushrod force.”
Pedal and brake-system modifications require appropriate design review — when that condition changes, compare separate calculator runs instead of blending the inputs.
Collecting the data in practice
Choose a controlled operating condition and record the setup before comparing a second run — this workflow must also account for the fact that geometry changes through pedal travel and friction reduces ideal force.
- Record Pivot-to-pedal distance as distance from pedal pivot to driver force application — measure from the stated reference points and note whether the vehicle or component is loaded.
- Record Pivot-to-pushrod distance as distance from pedal pivot to master-cylinder pushrod — measure from the stated reference points and note whether the vehicle or component is loaded.
- Record Driver pedal force as applied force at the pedal pad — use a measurement or specification from the exact component and operating condition being evaluated.
- Repeat the check only after accounting for this condition: geometry changes through pedal travel and friction reduces ideal force.
Questions about the formula and inputs
What measurement source fits Pivot-to-pedal distance when it represents distance from pedal pivot to driver force application?
Because pivot-to-pedal distance represents distance from pedal pivot to driver force application, use a source tied to the exact vehicle, component, and operating period described by the other fields.
How does the warning “Geometry changes through pedal travel and friction reduces ideal force” affect Pedal ratio?
The condition “Geometry changes through pedal travel and friction reduces ideal force” is not corrected automatically by the numeric inputs, so create a separate brake pedal ratio case when it changes.
What assumption is expressed by “pedal ratio = pivot-to-pad length ÷ pivot-to-pushrod length”?
In “pedal ratio = pivot-to-pad length ÷ pivot-to-pushrod length,” pivot-to-pedal distance and pivot-to-pushrod distance are treated as parts of one vehicle case.