How to use this calculator
- Enter spring rate. Use the installed spring rate.
- Enter motion ratio. Use spring travel divided by wheel travel.
- Set angle and mass. Add installation angle and sprung corner mass.
- Read rate and frequency. Review wheel rate and ride frequency.
How it works
The spring does not usually act directly at the wheel. This calculator defines motion ratio as spring travel divided by wheel travel, then applies installation angle: wheel rate = spring rate x (motion ratio x cos angle)^2. Ride frequency follows from f = 1/(2pi) x sqrt(k/m).
Use the corner weight calculator to get the corner mass context before choosing ride-frequency targets.
Worked example
Verified against the live calculator
A 50 N/mm spring with a 0.75 motion ratio and no angle correction gives about 28.1 N/mm at the wheel. With 350 kg sprung mass at that corner, ride frequency is about 1.43 Hz.
Frequently asked questions
What is wheel rate?
Wheel rate is the spring rate as seen at the wheel after motion ratio and installation angle are applied.
How is motion ratio defined here?
Motion ratio is spring travel divided by wheel travel. Wheel rate equals spring rate times effective motion ratio squared.
Why is motion ratio squared?
Suspension leverage affects both force and displacement, so rate changes with the square of the motion ratio.
Is ride frequency exact?
No. It is a linear sprung-mass estimate and does not include tires, bushings, damping, anti-roll bars, bump stops or progressive springs.
Method & assumptions
- Motion ratio is spring travel divided by wheel travel.
- Linear estimate excludes tires, bushings, damping, anti-roll bars, bump stops and progressive spring behavior.