| Spring Rate | Wheel Rate | Ride Frequency |
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Spring Rate, Wheel Rate, and Ride Frequency
Spring rate is how many pounds it takes to compress the spring one inch. But the spring rarely acts straight on the wheel, so the wheel rate — spring rate multiplied by the motion ratio squared — is what the tire actually feels. Combine wheel rate with the corner weight and you get ride frequency, the single best measure of how a suspension will ride and handle.
What Ride Frequency Tells You
Ride frequency is how quickly the sprung mass bounces, in cycles per second. Comfort cars live around 1.0 to 1.3 Hz, sporty street cars 1.3 to 1.7, track cars 1.7 to 2.2, and aero-dependent race cars beyond that. Matching your spring rate to a target frequency is how chassis tuners pick springs, rather than guessing.
Why Motion Ratio Matters So Much
Because wheel rate scales with the square of the motion ratio, a small change has a big effect. A 0.7 motion ratio means the wheel only feels about half the spring rate. Inboard pushrod suspensions and angled shocks all reduce the motion ratio, so always measure it rather than assuming 1.0.
Front-to-Rear Balance
For a flat ride over bumps, many setups run the rear ride frequency 10 to 20 percent higher than the front, so the rear catches up to the front after a bump. Track cars sometimes flip this for rotation. Use the target tool above to set each end deliberately.
Frequently Asked Questions
Should I use total corner weight or sprung weight?
Sprung weight — the corner weight minus the unsprung wheel, tire, and brake assembly. Unsprung mass is usually 10 to 15 percent of the corner.
What is a good street ride frequency?
Around 1.2 to 1.5 Hz balances comfort and control for most street cars. Stiffer feels sportier but harsher.
How do I find my motion ratio?
Measure how far the spring compresses for a known amount of wheel travel; motion ratio is wheel travel divided by spring travel.