Calculator Inputs
Use the responsive three, two, and one column field layout below.
Example Data Table
Example setup: 38 mm static ride height, 1.18 kg/m³ air density, 4.2 m² CLA, 42% axle balance, 90 N/mm springs, 1.10 motion ratio, and 110 N/mm tire stiffness.
| Speed (km/h) | Axle aero load (N) | Total drop (mm) | End ride height (mm) |
|---|---|---|---|
| 40 | 128.5 | 1.45 | 36.55 |
| 60 | 289.1 | 3.26 | 34.74 |
| 80 | 514.0 | 5.79 | 32.21 |
| 100 | 803.1 | 9.05 | 28.95 |
| 120 | 1,156.4 | 13.03 | 24.97 |
Formula Used
Faero,total = 0.5 × ρ × V² × (CLA)
Faxle = Faero,total × axle balance
Wheel Rate = Spring Rate / Motion Ratio²This page assumes motion ratio = wheel travel / spring travel.
Suspension Compression = Load Per Tire / Wheel RateTire Compression = Load Per Tire / Tire Stiffness
End Ride Height = Static Ride Height − Suspension Compression − Tire Compression
How to Use This Calculator
- Enter the axle label you want to study.
- Type the static ride height measured before the run.
- Enter the end-of-straight speed and choose its unit.
- Fill in air density and your aerodynamic CLA value.
- Set the share of total downforce carried by that axle.
- Enter spring rate, motion ratio, and tire stiffness data.
- Add any extra axle load if braking or ballast matters.
- Set your legal minimum ride height and bump stop gap.
- Press calculate to show the result above the form.
- Review the graph, margins, and export buttons.
FAQs
1) What does this calculator estimate?
It estimates axle ride height at the end of a straight using aerodynamic load, suspension compliance, tire compliance, and your chosen setup values.
2) Why is motion ratio important?
Motion ratio converts spring stiffness into wheel stiffness. A larger wheel-travel-to-spring-travel ratio lowers wheel rate and usually increases ride height loss under the same load.
3) Why is tire stiffness included?
The tire compresses under vertical load, just like the suspension. Ignoring tire stiffness can overestimate ground clearance and hide floor contact risk.
4) Should I use front or rear aero balance?
Use the load share for the axle you are checking. Front ride height needs front axle balance. Rear ride height needs rear axle balance.
5) Why does ride height change faster at higher speed?
Aerodynamic load scales with speed squared. That means a modest speed increase can create a much larger ride height drop near top speed.
6) What does a negative clearance margin mean?
It means the predicted end ride height falls below your limit. Raise static height, reduce aero load, stiffen the axle, or increase travel protection.
7) Can I include braking or extra vertical load?
Yes. Use the additional axle load field for extra heave, braking transfer, ballast effects, or any known vertical load you want included.
8) How should I improve clearance safely?
Start with verified measurements. Then adjust static height, spring rate, motion ratio, bump stop strategy, or aero balance in small steps. Recheck data after every setup change.