Suspension Sag
How to measure and set sag on forks and rear shocks for predictable handling, traction and comfort.
Overview
What is Sag?
Sag is the amount the suspension compresses under the rider's weight when stationary. It determines how much travel is available for both small bumps and bigger hits.
Why it Matters
Correct sag improves traction, balance and comfort. Too little sag makes the wheel skip; too much makes the bike wallow and bottom out.
Typical Targets
Common guidelines: forks 15–30% of travel; rear shocks 20–30% (trail and enduro bikes vary). Use manufacturer recommendations as a starting point.
Tools
Shock pump, measuring tool (ruler, tape or zip-tie), marker, helmet and your riding kit. A friend to help hold the bike is very useful.
Tip: Wear your normal riding kit and hydration pack when measuring — extra weight changes sag.
Step-by-Step: Set Your Sag
Put on your riding gear and any packs you normally carry. Make sure rebound is open and locks are off. Note factory recommended pressures for a starting point.
With the bike upright and unloaded, measure sag travel or mark a point on the stanchion/shaft. This tells you the full unloaded travel value.
Sit on the bike in riding position while a friend holds it upright. Gently bounce once and settle. Measure how far the suspension has compressed from unloaded to loaded position.
If sag is too little, reduce air pressure slightly; if too much, increase pressure in small increments. Re-measure after each adjustment until you hit your target percentage of travel.
Once sag is set, adjust rebound so the bike returns without oscillation. Add compression damping gradually if the bike bottoms too easily on big hits.
Ride a representative trail section and note handling. Small tweaks to pressure, rebound or compression are normal after a short test loop.
Common Mistakes
Show / hide common mistakes
- Measuring with wrong kit – Measuring without your normal gear or hydration changes sag results.
- Big pressure jumps – Large pressure changes can overshoot; adjust in small increments (5–10 psi or as manufacturer suggests).
- Forgetting to settle – Always bounce once and let the suspension settle before taking measurements.
- Ignoring recommended travel – Target sag is a percentage of travel; don't use an absolute mm value without checking total travel.
Practical Tips
- Use a zip-tie on the stanchion as a quick and accurate sag marker — make a small paint mark for a permanent line.
- Record starting pressures and measurements so you can return to a known baseline after experimentation.
- If your shock has a volume spacer option, use it to tune mid-stroke support without changing sag.
- Check sag when temperatures change — air pressure varies with temperature and affects sag.
Quick Practice Routine
Set sag before your first ride (10–20 min). After the first trail test, re-check and fine-tune rebound/compression (5–15 min). Re-verify after significant weight or kit changes.
Trail-Side Sag Tips
- Carry a compact shock pump and a zip-tie when travelling — quick adjustments can save a whole ride.
- If you suspect a leak (sag creeping over the ride), top up and check for punctures or loose Schrader/Presta valve cores where applicable.
- For remote ride days, keep a rough target pressure note for your bike and weight to recover quickly if pressures change.
Checklist
- Riding kit on
- Zip-tie or mark set
- Shock pump available
- Bench pressure recorded
Static measurement → Rider measurement → Pressure adjustments → Damping fine-tune → Trail validation
Where to Go Next
See our Rebound & Compression Tuning guide for optimizing your suspension performance after setting sag.