Spring Rate Conversion Calculator
Instantly convert suspension spring rates between kg/mm, lbs/in, and N/mm. Enter a value in any unit to see the equivalents.
Spring Rate Selection
Calculated frequencies assume simple undamped springs. Real suspension systems include dampers and anti-roll bars, which significantly affect ride behavior.
Work with a suspension tuner to select final spring rates for your specific car and driving goals.
Methodology
Natural Frequency: f = ¼π√(k/m) rad/s
k: Spring rate (lbs/in or N/mm)
m: Sprung mass (typically 1/4 vehicle weight)
Frequently Asked Questions
How do I know if spring rate is too high or too low?
Too soft = excessive body roll, poor turn-in response. Too stiff = poor grip (tires can't track surface), harsh ride, possible wheel liftoff. Street cars use 50-150 lb/in; race cars 200-500+ lb/in.
Should front and rear springs have different rates?
Yes. Typically rear is softer (more compliance) for mid-corner stability; front is stiffer (quicker response). Ratio depends on type (street: 1.2:1 front/rear; race: 1.1-1.5:1).
Can I change spring rate without upsetting anti-roll bar setup?
Not directly. Stiffer springs reduce roll naturally, allowing softer sway bars. Soften springs = stiffer bars needed. Change one variable at a time and measure results.
Disclaimer & Legal Notice
All tools and calculators provided by Lapsite are for informational and educational purposes only. While we strive for mathematical precision, these results are approximations and should not be used as the sole basis for critical engineering, financial, or safety decisions. Lapsite Ltd and its creators provide no warranty, express or implied, regarding the accuracy or fitness of these calculations for any specific use.Always double-check calculations independently, especially for safety-critical components such as brakes, suspension, or structural changes. By using these tools, you agree that Lapsite Ltd is not liable for any mechanical failure, financial loss, or injury resulting from the use of this data.
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