Sag is how much your suspension sinks under your bodyweight when you sit on the bike in riding position. It sets where in the travel you ride, and everything else, from grip to bottom-out resistance, follows from it. Get sag right and the clicks become fine-tuning. Get it wrong and no amount of clicking will save you.
Why sag comes first
Compression and rebound damping control how fast the suspension moves. But air pressure sets where it sits, and that is what sag measures. Two riders on the same bike with the same clicks but different sag are riding two completely different bikes.
- Too little sag (too much pressure): harsh, skips over bumps, no grip in corners.
- Too much sag (too little pressure): wallowy, blows through travel, vague on the pedals.
- Correct sag: supported but supple, the bike tracks the ground.
As a starting point most trail bikes want roughly 30% rear and 15–20% front. Your setup sheet stores these per bike so you never start from scratch.
Always set sag in full riding kit: pack, shoes, helmet. A loaded pack can shift your rear sag by 3–4%, which is a meaningful chunk of travel.
Setting it in ten minutes
Reset the o-ring
Slide the rubber o-ring on your fork stanchion and shock shaft down against the seal. No o-ring? A zip-tie works.
Get into position
Lean against a wall, clip in, and settle into a neutral attack position. Bounce gently once, then hold still.
Step off carefully
Dismount without compressing the suspension further. The o-ring now marks your sag.
Measure & adjust
Measure the exposed stanchion against total travel. Add air to reduce sag, release to increase it, then log it in Dialed.
"If a customer only does one thing, I tell them to set their sag. It fixes more problems than any tune I can sell them."
— A suspension tuner we work with
Sag targets by discipline
Starting points, not gospel. Heavier or more aggressive riders trend toward the firmer end of each range.
| Discipline | Front sag | Rear sag | Feel |
|---|---|---|---|
| XC / marathon | 12–15% | 25% | Firm, efficient |
| Trail | 15–20% | 30% | Balanced |
| Enduro | 18–22% | 30–33% | Planted, plush |
| Downhill | 20–25% | 33–38% | Maximum grip |
Too firm vs. too soft
✕ Too little sag
- Deflects off roots and rocks
- Hands and feet get hammered
- Front washes in flat corners
✓ Dialed sag
- Tracks the ground in the rough
- Grip on tap, mid-corner
- Travel left for the big hits
Sag changes as your air spring loses pressure over time. Re-check it every few rides, and always after a service. Log it in Dialed so you always know what you ran last.