How to Use the MTB Suspension Sag Calculator
Sag is how much your suspension compresses under your own weight the moment you sit on the bike. Getting sag right balances bump absorption against pedaling efficiency. Enter your rider weight, suspension travel, and whether you're setting up a front fork or rear shock, and this calculator returns your target sag percentage and a starting air pressure in psi.
As a general rule, front forks run 15-20% sag while rear shocks run 25-30% sag. Forks are typically set firmer for steering precision, while rear shocks are set a bit softer for traction and bump absorption.
Air pressure is estimated from your body weight in pounds multiplied by a coefficient specific to fork or shock. This is only a baseline starting point — actual riding style, terrain, and brand-specific spring curves usually call for fine-tuning within about ±10% of this value. After setting the pressure, measure your actual sag with a tape or o-ring and compare it against your target.
Frequently Asked Questions
Too little sag (suspension too firm) means poor bump absorption and a harsh ride. Too much sag (too soft) causes excessive suspension movement during cornering and pedaling, wasting energy.
No. This is a starting baseline. Actual riding style, terrain, and brand-specific spring curves usually call for fine-tuning within about ±10% of this value.