Mountain Bike Suspension Setup — Sag, Rebound, Compression
Buying a bike with good suspension is half the job. The other half is setting it up for you — factory settings rarely match your weight and riding style, and a few minutes of adjustment changes how the bike behaves completely.
Sag — the starting point
Sag is the percentage of suspension travel that compresses under your weight (full kit, pack included). It's the most important parameter — everything else starts from here.
| Riding style | Front sag | Rear sag |
|---|---|---|
| Cross-country (XC) | 15–20% | 20–25% |
| Trail / all-mountain | 20–25% | 25–30% |
| Enduro / DH | 25–30% | 30–35% |
How do I measure sag?
Set the suspension to fully open (all dials in "open" position). Slide the rubber O-ring on the stanchion all the way down. Sit on the bike in your natural riding position — feet on the pedals, hands on the bars. Have someone hold the bike steady. Carefully dismount without disturbing the suspension. Measure how far the O-ring moved. Divide by total travel — that's your sag percentage. Adjust sag with air pressure (air shocks) or spring rate (coil shocks).
Rebound
Rebound controls how fast the suspension returns to full extension after being compressed. The dial is usually marked with a turtle (slower) and a hare (faster).
- Too fast rebound — the bike "bucks" over bumps and loses traction.
- Too slow rebound — the suspension can't keep up with consecutive hits, "packs down," and loses travel.
Test: roll off a curb. The bike should rebound once and settle. If it bounces, slow the rebound down. If it returns sluggishly, speed it up.
Compression
Compression controls resistance as the suspension compresses. It splits into two categories:
- Low-speed compression (LSC) — affects behavior during slow movements: pedal bob, cornering lean. Adding LSC reduces bob.
- High-speed compression (HSC) — affects behavior during fast impacts: rocks, roots, drops. Adding HSC firms up the suspension against hard hits.
Cheaper shocks have a single compression dial (or a lockout). More expensive ones separate LSC and HSC.
When should I use the lockout?
Lockout locks the suspension solid — useful on long, smooth climbs where suspension bob wastes energy. Always unlock for descents and technical terrain.
Bottom line: start with sag, dial in rebound with the curb test, then fine-tune compression to your terrain. A properly set-up fork or shock changes how a bike handles more than most component upgrades.