Calculator Inputs
Example Data Table
| Corner | Measured Height | Target Height | Motion Ratio | Thread Pitch | Spring Rate |
|---|---|---|---|---|---|
| FL | 112 mm | 115 mm | 1.650 | 1.50 mm/turn | 90 N/mm |
| FR | 113 mm | 115 mm | 1.650 | 1.50 mm/turn | 90 N/mm |
| RL | 124 mm | 126 mm | 1.720 | 1.50 mm/turn | 110 N/mm |
| RR | 125 mm | 126 mm | 1.720 | 1.50 mm/turn | 110 N/mm |
Formula Used
1. Wheel correction for each corner:
Wheel Correction = Target Height − Measured Height
2. Spring seat travel using wheel-to-spring motion ratio:
Seat Travel = Wheel Correction ÷ Motion Ratio
3. Required threaded perch rotation:
Perch Turns = Seat Travel ÷ Thread Pitch
4. Front and rear axle averages:
Front Average = (FL + FR) ÷ 2
Rear Average = (RL + RR) ÷ 2
5. Rake calculation:
Rake = Rear Average − Front Average
6. Optional wheel rate estimate:
Wheel Rate = Spring Rate ÷ (Motion Ratio²)
These formulas assume linear suspension response around the measurement range and a consistent thread pitch across the corresponding axle.
How to Use This Calculator
- Measure ride height at each corner using one repeatable reference point.
- Enter your target ride heights for FL, FR, RL, and RR.
- Enter the wheel-to-spring motion ratio for each corner.
- Add front and rear thread pitch values from the perch hardware.
- Optionally enter spring rates to estimate wheel rates and load change.
- Click Calculate Ride Height to see averages, rake, seat travel, and perch turns.
- Review the Plotly graph to compare measured, target, and predicted values.
- Download the calculation as CSV or PDF for workshop records.
FAQs
1) What does this ride height calculator measure?
It compares measured and target heights at all four corners, then estimates seat travel, perch turns, axle averages, and front-to-rear rake changes.
2) Why is motion ratio important?
Ride height changes at the wheel are not equal to spring seat movement. Motion ratio converts wheel correction into the spring-side adjustment you actually need.
3) What is rake in suspension setup?
Rake is the rear average ride height minus the front average ride height. It affects balance, aero attitude, steering response, and weight transfer behavior.
4) Should I use millimeters or inches?
Either works. Stay consistent. Measured heights, target heights, and thread pitch must all use the same length unit for correct perch-turn results.
5) What does positive perch travel mean?
In this calculator, positive seat travel means raising the spring seat. Negative travel means lowering it. Follow your suspension hardware direction marks before adjusting.
6) Why are spring rates optional?
Spring rates are only needed for the optional wheel-rate and estimated load-change outputs. Core ride height, seat travel, and perch turn calculations work without them.
7) Can this replace corner-weight scales?
No. It is useful for ride-height targeting and repeatable perch estimates, but actual corner weights, tire pressures, fuel load, and driver weight still matter.
8) Why might real results differ from predicted values?
Bushing friction, binding, tire growth, platform preload, imperfect references, nonlinear linkage geometry, and surface level differences can all shift final ride height.