RockShox Coil Spring Rate Calculator
Use this tool to estimate a starting rear shock coil spring rate (lb/in and N/mm) for RockShox Super Deluxe Coil and Vivid Coil setups.
If you have ever gone down the spring-rate rabbit hole, you know how quickly it gets confusing: rider weight, bike kinematics, leverage curves, preload, and sag targets can all pull your setup in different directions. This RockShox spring calculator gives you a practical baseline so you can get close on the first try, then fine-tune on trail.
Why coil spring rate matters
For a coil shock, the spring rate is your foundation. Too light and you sit too deep in travel, pedal poorly, and blow through on bigger hits. Too stiff and the bike can feel harsh, skittery, and reluctant to settle into corners. Proper spring rate gets your dynamic ride height where it belongs so damping adjustments actually make sense.
- Correct sag helps keep geometry balanced.
- Better traction comes from stable wheel loading.
- Damping range improves because rebound and compression are working from a sensible spring platform.
How this RockShox spring calculator works
The calculator estimates a required spring rate using static load at the rear wheel, leverage ratio, target shock sag, and preload compression. It then maps your value to common RockShox-compatible spring increments (usually in 25 lb/in steps).
Inputs explained
- Rider + gear weight: Include pack, shoes, water, and anything you ride with.
- Bike weight: Full ride-ready weight.
- Rear weight bias: Your load distribution at the rear axle. Seated climbing is often higher than standing descending.
- Shock stroke: Printed on the shock size (for example 230x65 means 65 mm stroke).
- Leverage ratio: Wheel travel divided by shock stroke (for example 180 mm travel / 65 mm stroke ≈ 2.77).
- Target sag: Most enduro and DH setups land around 27–33%.
- Preload: Collar compression added before load; usually keep this modest.
Quick spring-rate reference
| Spring Rate (lb/in) | Approx. N/mm | Typical Rider Use Case |
|---|---|---|
| 350 | 61.3 | Lighter riders or lower leverage frames |
| 400 | 70.1 | Mid-weight trail/enduro baseline |
| 450 | 78.8 | Common all-around enduro value |
| 500 | 87.6 | Heavier riders or firmer setup preference |
| 550 | 96.3 | Aggressive riding, high loads, or bike-park focus |
How to fine-tune after your first ride
1) Check sag accurately
Wear full riding kit, stand in a neutral attack position, and bounce lightly to break friction. If your measured sag differs from target by more than about 2–3%, move one spring step up or down.
2) Keep preload reasonable
If you need excessive preload to hit sag, the spring is probably too light. As a practical rule, keep preload low and let spring rate do the heavy lifting.
3) Rebound comes next
Once spring rate and sag are right, set rebound for control without pack-down. A heavier spring typically needs more rebound damping.
4) Use volume and damping for feel
After spring and rebound, tweak low-speed compression for support and high-speed behavior for harsh impacts. Spring rate is not the right tool for every feel issue.
FAQ
Should I size spring by bodyweight alone?
No. Weight is only one variable. Leverage ratio, sag target, preload, and riding position all influence required spring rate.
Can I use this for non-RockShox coil shocks?
Yes as a baseline, since spring-force math is universal. Just verify stroke length and available spring standards for your specific shock.
What if I’m between spring sizes?
Choose based on your priority: more sensitivity (lower rate) or more support and bottom-out margin (higher rate). Rider style and terrain should decide.
Final thoughts
A good spring rate transforms the bike. This tool helps you skip the guesswork and start in the right zone, especially when building a new bike or converting from air to coil. Run the calculator, pick the nearest available RockShox spring, and then refine with real trail feedback.