Ridetech Spring Rate Calculator

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Ridetech Spring Rate Calculator

Optimize Your Suspension Geometry & Handling

The scale weight of a single wheel.
Spring distance from pivot / Control arm length.
Angle from vertical (0 is perfectly vertical).
Effective rate felt at the tire.

Calculated Spring Rate

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lbs/in

Understanding Ridetech Spring Rates

Choosing the correct spring rate is the most critical step in setting up a performance suspension system, whether you are running Ridetech coilovers or Shockwaves. The spring rate determines how much weight is required to compress the spring by one inch. However, the Effective Wheel Rate—what the car actually feels—is significantly different from the rate printed on the spring due to leverage and mounting angles.

Key Calculation Factors

  • Corner Weight: This is the total load on an individual tire. For a balanced street car, this is usually 25% of the total vehicle weight, though front-heavy vehicles will differ.
  • Motion Ratio: Because the spring is usually mounted partway down the control arm, it has a mechanical disadvantage. If the spring is halfway between the pivot and the ball joint, the motion ratio is 0.5. Squaring this ratio is necessary to find the rate conversion.
  • Shock Angle: As a shock leans over, it becomes less efficient. A 20-degree tilt significantly reduces the spring's ability to support the load compared to a vertical mount.
  • Wheel Rate: This is your target. Performance street cars typically aim for a wheel rate that results in a natural frequency of 1.2Hz to 1.5Hz. High-performance track cars may go up to 2.0Hz or higher.

Example Calculation

Suppose you have a classic muscle car with the following specs:

Variable Value
Corner Weight 800 lbs
Motion Ratio 0.65
Shock Angle 10 Degrees
Target Wheel Rate 140 lb/in

Using the formula, the required spring rate would be approximately 336 lbs/in. In this scenario, you would likely select a standard 350 lb Ridetech spring for your coilover setup.

Coilover vs. Shockwave

When using Ridetech Shockwaves (air suspension), the "spring rate" is adjustable by changing air pressure. However, the physical dimensions and bellows style (Rolling Sleeve vs. Double Convoluted) still provide a baseline rate. This calculator helps you determine the "Equivalent Linear Rate" you should aim for when the vehicle is at its defined Ride Height.

function calculateSpringRate() { var weight = parseFloat(document.getElementById('cornerWeight').value); var mr = parseFloat(document.getElementById('motionRatio').value); var angle = parseFloat(document.getElementById('shockAngle').value); var targetWR = parseFloat(document.getElementById('wheelRate').value); var resultDiv = document.getElementById('springResult'); var resultValue = document.getElementById('springRateValue'); var warningDiv = document.getElementById('frequencyWarning'); if (isNaN(weight) || isNaN(mr) || isNaN(angle) || isNaN(targetWR) || mr <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // Convert angle to radians var angleRad = angle * (Math.PI / 180); // Spring Rate Formula: SR = WheelRate / (MR^2 * cos(angle)) // We use cos(angle) for the vertical component efficiency var cosAngle = Math.cos(angleRad); // SR = WheelRate / (MR^2 * Cos(Angle)) var calculatedSR = targetWR / (Math.pow(mr, 2) * cosAngle); // Calculate Natural Frequency for additional context // Frequency (Hz) = 3.13 * sqrt(WheelRate / CornerWeight) var freq = 3.13 * Math.sqrt(targetWR / weight); resultValue.innerHTML = Math.round(calculatedSR); resultDiv.style.display = 'block'; var freqText = "Estimated Natural Frequency: " + freq.toFixed(2) + " Hz. "; if (freq = 1.0 && freq 1.5 && freq <= 2.2) { freqText += "(Firm, suitable for autocross/track use)"; } else { freqText += "(Extremely stiff, race-only application)"; } warningDiv.innerHTML = freqText; }

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