Rear Shock Spring Rate Estimator
Use this tool to estimate a starting spring rate for an Öhlins-style rear shock setup. Enter your values, then fine-tune with real sag measurements.
Why Spring Rate Matters
Spring rate is one of the biggest factors in how your bike feels under braking, acceleration, and cornering. A spring that is too soft can cause excessive squat, vague front-end feel, and bottoming. A spring that is too stiff can reduce grip and make the ride harsh over imperfect pavement.
The goal is simple: choose a spring that places your suspension in the right operating range so damping adjustments can do their job. If spring is wrong, clickers often cannot fully fix the behavior.
How This Öhlins Spring Rate Calculator Works
This tool estimates the rear spring needed to hit a target rider sag. It uses:
- Total load (bike + rider + added gear/passenger)
- Estimated rear weight bias by bike type
- Target rider sag percentage
- Linkage motion ratio (wheel travel divided by shock travel)
- A riding-style multiplier to bias slightly softer or firmer
Output is shown in the three most common formats: N/mm, kg/mm, and lb/in.
Formula Summary
- Rear load force = (total mass × rear bias) × 9.80665
- Wheel sag target (mm) = travel × sag %
- Wheel rate = rear force ÷ sag target
- Shock spring rate = wheel rate × (motion ratio²) × usage factor
How to Use Your Result
1) Pick the closest available spring
If the calculator returns 96.7 N/mm, a 95 or 100 N/mm spring is usually the practical choice. Most riders should choose the closest option and then verify sag with preload.
2) Measure rider sag after installation
The calculator gives a starting point. Final setup should be based on real measurements with your normal riding kit.
- Street setup target: roughly 28–33% rear rider sag
- Track setup target: roughly 24–30% rear rider sag
- Touring loaded bikes may run slightly more preload with similar sag goals
3) Adjust damping only after spring is close
Once spring and preload are in range, then tune rebound and compression. This sequence prevents chasing setup problems with clickers alone.
Common Mistakes to Avoid
- Ignoring gear weight: helmet, suit, backpack, and tools can add significant load.
- Using dry bike weight: wet weight gives better real-world estimates.
- Guessing motion ratio: if possible, use manufacturer or measured linkage data.
- Confusing units: N/mm, kg/mm, and lb/in are not interchangeable without conversion.
- Over-focusing on one number: spring rate is foundational, but geometry and damping still matter.
FAQ
Is this an official Öhlins calculator?
No. It is an independent estimator designed to help riders choose a sensible starting spring.
Can I use this for track-only bikes?
Yes. Select an aggressive usage mode and a lower sag target within your race setup range, then validate at the circuit.
What if my current spring is listed?
Enter your current spring and unit. The tool will estimate whether you are likely too soft or too stiff and show an estimated rider sag from that spring.
Final Note
A great suspension setup starts with the correct spring. Use this calculator to narrow your options quickly, then finish the job with proper measurements and test rides. That combination is what turns a bike from “acceptable” into truly confidence-inspiring.