Repair guides › Suspension
Set rear shock sag
The rear spring and damper on a full-suspension bike. Air pressure is the spring; oil flowing through valves is the damper. Linkage pivots let the rear wheel move.
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Tools
- Tape measure + 6" steel ruler: Stanley 16 ft tape measure ($)
- Shock pump: RockShox High Pressure Shock Pump ($$)
- Sag O-rings (suspension setup): ZDBB rubber O-ring assortment kit ($)
Compare Good, Better and Best for each tool
Steps
- Find shock stroke length (printed on the shock).
- Set the climb switch or compression open. Set pressure to about your weight in pounds as a start.
- Remove the pump, then compress the shock about 15% of its travel a few times to equalize the air chambers, and re-check the pressure.
- Push the O-ring to the seal, sit on the bike in riding position, get off gently.
- Aim for 25–30% sag of stroke (RockShox: 25% for Solo Air, 30% for DebonAir, ±5%).
- Adjust air in 5 psi steps. Never compress the shock with the pump attached.
Diagram
Side view, chain side toward youFork
Signs it needs doing
- Too much bob when pedaling
- Harsh bottom-out
- Loss of air overnight