QA1 Spring Rate Calculator
Recommended QA1 Spring Rate
Estimated Ideal Rate: 0 lbs/in
Wheel Rate (Stiffness at the tire): 0 lbs/in
*Always round to the nearest available QA1 spring increment (e.g., 250, 275, 300).
How to Use the QA1 Spring Rate Calculator
Choosing the correct spring rate for your coilovers is critical for achieving the desired ride quality and handling performance. This calculator uses automotive suspension geometry to translate your vehicle's weight and mounting position into a specific spring rate recommendation compatible with QA1 systems.
Understanding the Variables
- Corner Weight: This is the weight of the vehicle sitting on one specific tire. For the most accurate results, use vehicle scales.
- Unsprung Weight: The weight of components not supported by the spring (wheels, tires, brakes, half the control arm weight). A common estimate is 75-120 lbs depending on the vehicle.
- Motion Ratio: The leverage the control arm has over the spring. In an A-arm suspension, it is calculated by measuring the distance from the inner pivot to the spring mount divided by the distance from the inner pivot to the ball joint.
- Spring Angle: If your coilovers are tilted, they lose efficiency. A vertical spring has a 0-degree angle.
The Math Behind the Spring
The core physics relies on determining the "Wheel Rate"—the actual stiffness felt at the tire. The formula used is:
Wheel Rate = [Spring Load × (2 × π × Frequency)²] / 386.4
Spring Rate = Wheel Rate / (Motion Ratio² × cos(Angle))
Example Calculation
Imagine a classic muscle car with the following specs:
- Corner Weight: 900 lbs
- Motion Ratio: 0.5 (Common for GM A-bodies)
- Angle: 10 degrees
- Desired Ride Frequency: 1.5 Hz (Moderate Street)
In this scenario, the calculator would determine the wheel rate needed to support the mass at that frequency, then adjust for the 0.5 motion ratio (which squares to 0.25), resulting in a significantly higher spring rate (e.g., 450-550 lbs) than the weight itself would suggest.
Why QA1 Springs?
QA1 springs are manufactured using high-tensile chrome silicon wire, which allows for fewer coils and a lighter weight compared to standard steel springs. This reduces unsprung weight and prevents "spring bind," ensuring your suspension travels through its full range smoothly. When selecting your final spring, ensure the spring length matches your coilover body height to prevent the spring from unseating at full extension.