fox suspension calculator

How to Use This FOX Suspension Calculator

This calculator gives you a reliable baseline for FOX air spring settings. It combines rider system weight, sag targets, leverage ratio, and riding style to estimate starting pressure for your fork and rear shock. A good baseline saves time and helps you get to trail-ready suspension faster.

Suspension setup is always a process, not a one-click answer. Use these numbers as your first pass, then refine based on trail feel, O-ring position, and repeated test laps.

What the Calculator Outputs

• Fork pressure (PSI): Starting air pressure based on total riding weight, bike category, terrain, and fork sag target.
• Rear shock pressure (PSI): Starting air pressure using leverage ratio and rear sag target.
• Sag in millimeters: Fork and rear wheel sag values so you can verify with an O-ring measurement.
• Shock sag (mm): Sag at the shock shaft itself, useful for precision setup.
• Rebound click suggestions: A practical first setting from fully closed.
• Volume spacer guidance: Basic recommendation for support vs. sensitivity.

Recommended Sag Targets for FOX Trail Bikes

Fork Sag Guidelines

• XC: 15% to 20%
• Trail: 18% to 22%
• Enduro: 20% to 25%

Rear Sag Guidelines

• XC: 22% to 27%
• Trail: 27% to 32%
• Enduro: 28% to 33%

If you ride extremely rough terrain or prefer maximum grip, run sag toward the upper end of each range. If you want a firmer, poppier bike for pumping and jumping, run closer to the lower end.

Step-by-Step: Dialing In After You Calculate

1) Set Air Pressure

Use a shock pump and match the suggested PSI values. Cycle suspension through part of its travel a few times and recheck pressure.

2) Verify Sag

In full riding kit, stand in neutral attack position and carefully settle your weight on the bike. Check O-ring displacement and compare to target sag in millimeters.

3) Set Rebound

Start from the click recommendations. Too fast feels bouncy and unstable; too slow feels dead and packs down in repeated hits.

4) Fine-Tune Compression and Volume Spacers

If you are using too much travel too easily, add pressure in small steps (2 to 4 PSI), add low-speed compression, or consider more volume spacers. If your ride is harsh and traction is poor, reduce pressure slightly or open compression.

Common Setup Mistakes to Avoid

• Measuring body weight without gear, water, and tools.
• Skipping sag verification after changing pressure.
• Changing multiple knobs at once, making feedback unclear.
• Ignoring tire pressure when evaluating suspension performance.
• Using one short ride to judge setup instead of repeated test sections.

Important Notes

This fox suspension calculator provides a starting point, not a guaranteed final tune. Exact pressure requirements vary by frame kinematics, riding posture, spring curve, and personal preference. Always check your FOX fork and shock manuals for service intervals, pressure limits, and model-specific tuning instructions.