How to set MTB SAG: guide, chart & tips
SAG is the most important basic setting on any full-suspension mountain bike. If it is wrong, even the best damping settings will not help much. Here you will learn what SAG is, which value suits your riding and how to set it yourself in 15 minutes.
What is SAG?
SAG is the negative travel: the part of the travel that the fork and shock already use when you simply stand on the bike with your body weight and kit. It is given as a percentage of total travel.
SAG allows the suspension not only to compress but also to extend into dips and holes. The tyres keep contact with the ground, the bike feels calmer and the geometry stays the way the frame designer intended. Too little SAG makes the bike harsh and nervous; too much makes it wallow, spoils the climbing geometry and leads to frequent bottom-outs.
SAG chart by riding style
The following values are proven starting points. If the manufacturer of your frame or shock specifies its own target SAG, that always takes priority – modern rear ends are often tuned for one specific value.
| Riding style | Typical travel | Fork SAG | Shock SAG |
|---|---|---|---|
| Cross-country (XC) | 100–120 mm | 15–20 % | 20–25 % |
| Downcountry / trail | 120–150 mm | 18–22 % | 25–30 % |
| All-mountain | 150–160 mm | 20–25 % | 28–30 % |
| Enduro | 160–180 mm | 20–25 % | 28–33 % |
| Downhill / bike park | 180–200 mm | 20–25 % | 30–35 % |
| E-MTB (trail/enduro) | 140–180 mm | 20–25 % | 28–30 % |
Tip: our suspension calculator works out suitable starting pressures from your weight and your bike and shows the SAG directly in millimetres.
Setting SAG – step by step
You need a shock pump with a gauge, a ruler or calliper and ideally a second person or a wall to lean against.
- Put on your kit. Stand on the bike with everything you normally ride with: helmet, shoes, backpack with a full hydration bladder, pads. That can easily add 4–8 kg.
- Set the base pressure. Pump the fork and shock to the starting value from the sticker on the stanchion, the manufacturer’s recommendation or our calculator. Open the compression (compression or platform lever to “open”).
- Equalise the air chambers. After pumping, cycle the suspension a few times without sitting on the bike so that the positive and negative chambers equalise. Check the pressure again afterwards.
- Get on. Stand on the pedals in your normal riding position – for the rear, seated or standing depending on the manufacturer’s advice; for the fork, standing in the attack position. Bounce gently a few times, then come to rest.
- Set the O-ring. Ask your helper to push the O-ring on the stanchion or shock shaft all the way to the seal. Alternatively, push it to the seal beforehand and then get on carefully.
- Get off carefully without compressing the suspension any further.
- Measure. Measure the distance between the seal and the O-ring. Divide it by the travel (fork) or the shock stroke (not the rear-wheel travel!).
- Correct. If the value is too high, add pressure in steps of 5 psi (0.34 bar) at the fork and 10 psi (0.69 bar) at the shock. If it is too low, let some air out. Repeat the measurement until you reach the target value.
The fork
Many forks (e.g. RockShox Pike, Lyrik, ZEB or FOX 36/38) have a percentage scale on the stanchion so you can read the SAG directly. Most manufacturers recommend 15–25 % for trail and enduro forks. On coil forks, SAG can only be changed via the spring rate and, within narrow limits, the preload.
The fork is harder to measure exactly because your weight shifts as you get off. It is better to measure two or three times and take the average.
The shock
What matters is the ratio to the shock stroke. The dimensions are usually printed on the shock or listed in the bike’s spec sheet, e.g. “210 × 55” (eye-to-eye length × stroke in mm). With trunnion and metric shocks, some manufacturers have special SAG indicators on the frame or rocker link. Coil shocks are set up with the right spring rate; preload should only be 1–2 turns.
Common mistakes when setting SAG
- Measuring without your kit – the backpack alone can change SAG by several percent.
- Compression closed – a closed lockout or climb mode distorts the measurement.
- Travel instead of shock stroke – at the rear, what counts is the stroke at the shock, not the travel at the wheel.
- Chambers not equalised – always cycle the suspension several times after pumping and recheck the pressure.
- Pump loses air when unscrewed – the hiss usually comes from the pump hose, not the air chamber. Still, it is better to set the pressure slightly higher and measure again.
Fine-tuning after SAG
Once SAG is set, rebound comes next: it determines how quickly the suspension extends again. Basic rule: the higher the air pressure, the slower the rebound should be set. After that you can fine-tune progression with compression and volume spacers. If you never use full travel on your local trails, remove a spacer; if the suspension often bottoms out hard, add one.
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