Coilover Spring Rate Calculator

Coilovers need a spring rate matched to your suspension geometry — not just your car's weight. Enter your corner weight, unsprung weight, suspension geometry dimensions (Dimension A, Dimension B, and coilover angle), wheel travel, and target wheel rate into the Coilover Spring Rate Calculator to find the Required Spring Rate for your coilover spring. Secondary outputs include motion ratio, effective wheel rate, and natural frequency.

lbs

Weight at one corner of the vehicle including sprung weight

lbs

Weight of wheels, brakes, control arms not supported by springs

inches

Distance from control arm pivot to spring centerline

inches

Distance from control arm pivot to ball joint centerline

degrees

Angle of coilover from vertical (0 = vertical)

inches

Total vertical wheel travel

lbs/in

Desired wheel rate for handling characteristics

Results

Required Spring Rate

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Motion Ratio

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Effective Wheel Rate

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Natural Frequency

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Frequently Asked Questions

What is motion ratio and why is it important?

Motion ratio is the relationship between wheel movement and spring/shock movement. It affects how spring rate translates to wheel rate. A lower motion ratio means the spring rate needs to be higher to achieve the same wheel rate.

How do I measure dimension A and B on my suspension?

Dimension A is measured from the control arm pivot point to directly under the spring centerline. Dimension B is from the pivot point to the ball joint centerline. Use a measuring tape and ensure the suspension is at ride height.

What's the difference between spring rate and wheel rate?

Spring rate is the force required to compress the spring one inch. Wheel rate is the force at the wheel required to move it one inch vertically. Motion ratio converts between these two values.

How does coilover angle affect spring rate calculations?

Angled coilovers reduce the effective spring rate because the spring doesn't work directly vertically. The calculation accounts for this angle to determine the actual spring rate needed.

What spring rate should I choose for street driving vs racing?

Street driving typically uses lower spring rates (100-200 lbs/in wheel rate) for comfort. Racing applications use higher rates (200-400+ lbs/in) for better handling and reduced body roll.

How do I determine my vehicle's corner weight?

Use corner scales or visit a racing shop with scales. Alternatively, divide total vehicle weight by 4 and adjust for weight distribution (front/rear bias and left/right balance).