Ride Height & Spring Preload Calculator
Calculate the exact collar adjustment needed to raise or lower your car without re-corner-weighting.
Negative to lower, positive to raise (-0.5 = Drop half inch).
Turn Estimate (12 TPI Coilover)
Rotate collar 5.1 turns DOWN (spin perch lower). Check your specific collar pitch; 12 TPI (threads per inch) or 2.0mm pitch is very common.
Adjusting Coilovers Properly
This calculator is for independently adjustable or non-adjustable-body coilovers where you adjust the main spring perch.
- Double-adjustable bodies: If your lower mount threads independently, you do not need to touch the spring perch to change height (maintaining identical bump/droop travel).
- Changing single-perch height alters your bump-to-droop ratio.
- Ensure you DO NOT hit coil-bind (spring bottoms out before bump stop).
Methodology
Collar Adjustment: Target_Ride_Height_Δ × Motion_Ratio
Because the spring is mounted inboard on a control arm (motion ratio), lowering the spring collar by 1 inch lowers the wheel by MORE than 1 inch (Wheel_Δ = Spring_Δ ÷ MR). This calculator reverses that math so you know exactly how far to spin the collar to get a desired fender height.
Frequently Asked Questions
Will moving my spring perch ruin my corner balance?
If you move all four perches equally (adjusting the whole car down 0.5 inches), your cross weight percentage will barely change. However, adjusting just one corner WILL dramatically alter your cross weights (jacking weight diagonally). You should only use this to hit a baseline height before putting the car on scales.
What is zero preload?
Zero preload means the spring is captive (snug) against the perches when the suspension is at full droop (car lifted), but not compressed. Preloading the spring does NOT make the static car sit higher with 'stiffer' springs; it only alters droop travel. True ride height is determined by where the perch sits.
How do I measure my motion ratio?
Remove the spring. Jack the wheel up 1 inch. Measure how far the shock piston compressed. If it compressed 0.8 inches, your motion ratio is 0.8.
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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