RZR Spring Rate Calculator
Calculate the optimal spring rate for your Polaris RZR based on weight, motion ratio, and desired ride frequency.
Total weight on one wheel minus unsprung weight (wheel/tire/hub).
Shock Travel ÷ Wheel Travel (Typical RZR: 0.55 – 0.75).
1.0 Hz – Soft Rock Crawling
1.2 Hz – Comfort / Trail
1.5 Hz – Aggressive Trail (Recommended)
2.0 Hz – Desert Racing
2.5 Hz – Short Course / Jumping
Determines suspension stiffness and response speed.
Amount the spring is compressed at full droop.
Recommended Spring Rate
– lbs/in
Wheel Rate (Effective stiffness at the tire)
– lbs/in
Estimated Load at Ride Height
– lbs
How to Choose the Right RZR Spring Rate
Upgrading the suspension on your Polaris RZR is one of the most effective modifications you can make. However, buying expensive shocks or springs won't help if the spring rate is incorrect for your specific vehicle setup. This calculator helps you determine the ideal spring rate (measured in lbs/in) based on physics, rather than guessing.
Key Inputs Explained
- Sprung Corner Weight: This is the weight resting on a specific corner of the vehicle, excluding the unsprung weight (tire, wheel, hub, brake assembly, and half the control arm). For a stock RZR XP 1000, typical unsprung weight is around 80-100 lbs per corner. If your total corner scale weight is 500 lbs, your "Sprung" weight is approximately 400 lbs.
- Motion Ratio (MR): This is the mechanical advantage of the suspension arm. It is the ratio of Shock Travel to Wheel Travel.
- If the wheel moves 1 inch and the shock moves 0.7 inches, the MR is 0.7.
- Typical RZR Motion Ratios: RZR XP 1000 Front (~0.60), Rear (~0.70). These vary by year and aftermarket arm geometry.
- Target Frequency (Hz): This measures how fast the suspension oscillates.
- 1.0 – 1.2 Hz: Plush ride, slow reaction. Good for slow rock crawling.
- 1.5 – 1.8 Hz: The "Sweet Spot" for most recreational drivers. Good mix of bump absorption and body roll control.
- 2.0+ Hz: Race stiffness. Required for high-speed whoops and large jumps to prevent bottoming out.
The Math Behind Suspension Tuning
This calculator uses the natural frequency formula to derive the required spring rate. The physics formula used is:
Wheel Rate = (Sprung Weight / 386.4) × (Frequency × 2π)²
Once the Wheel Rate is known, we calculate the Spring Rate required to achieve that stiffness at the wheel, accounting for the mechanical leverage (Motion Ratio):
Spring Rate = Wheel Rate / (Motion Ratio)²
Adding Weight (Passengers & Accessories)
One of the main reasons RZR owners upgrade springs is "Spring Sag." Over time, stock springs lose their tension, or you add weight such as:
| Item | Estimated Weight |
|---|---|
| Aftermarket Cage | +50 to +100 lbs |
| Spare Tire & Mount | +40 to +60 lbs |
| Cooler (Full) | +30 to +50 lbs |
| Tools & Recovery Gear | +20 to +40 lbs |
When adding this weight, your ride height decreases. While you can add preload to regain height, you are eating into your droop travel. A heavier spring rate is the correct fix to support the added load while maintaining proper suspension geometry.