The foundation of suspension setup
Sag is the amount your suspension compresses under your body weight when you're in your normal riding position. It's measured as a percentage of total travel and is the single most important suspension setting to get right. Think of it as the baseline that determines how your suspension will react to everything else on the trail.
| Suspension Type | Recommended Sag | Notes |
|---|---|---|
| Front Fork (Trail/Enduro) | 20-25% | Start at 20%, increase for more traction |
| Front Fork (DH/Gravity) | 25-30% | Higher sag for better bump absorption |
| Rear Shock (Air) | 25-30% | Most common starting point |
| Rear Shock (Coil) | 30-35% | Coils need more sag for proper feel |
Position the O-ring (or zip-tie) on the shock shaft or fork stanchion all the way down against the seal. Make sure your suspension is fully extended and clean.
Wearing your full riding gear (pack, water, etc.), carefully mount the bike in your normal riding position. For the most accurate measurement:
Without compressing the suspension further, carefully step off the bike. The O-ring should now show how much the suspension compressed under your weight.
Measure the distance from the O-ring to the seal. This is your sag measurement.
Sag % = (Sag Distance ÷ Total Travel) × 100
Example: 40mm sag on a 160mm shock = (40 ÷ 160) × 100 = 25% sag
Use a high-pressure shock pump to adjust:
Unlike air shocks, coil springs come in different spring rates (measured in lb/in or N/mm). You'll need to select the correct spring rate for your weight. Most manufacturers provide spring rate charts.
Consult your shock manufacturer's spring rate chart based on your weight (including gear). Most riders fall into these categories:
Follow the same measurement process as air suspension: position O-ring, mount bike in riding position, dismount carefully, and measure the distance. Target 30-35% sag for coil shocks.
Most coil shocks have a preload adjuster collar. However:
⚠️ Important
Preload should only be used for minor adjustments (±5mm). If you need more than 2-3 turns of preload to achieve proper sag, you need a different spring rate. Excessive preload reduces small-bump sensitivity.
Having someone hold the bike while you mount and dismount makes the process much easier and more accurate.
If you're alone, lean the bike against a wall or doorframe to help stabilize it during measurement.
Take 2-3 measurements and average them for the most accurate result. Small variations are normal.
Look at your O-ring after rides to see how much travel you're using. This helps you understand if your sag is appropriate for your riding style.
Air pressure changes with temperature. Check your sag if you're riding in significantly different conditions than when you set it up.
Keep a log of your air pressures or spring rates. This makes it easy to return to a known good setup.
This usually means you have too much sag. Try:
You likely have too little sag. Try:
For air shocks, this is normal due to:
For air shocks:
For coil shocks:
Once you've dialed in your sag, you're ready to move on to rebound and compression damping adjustments. These settings work together with sag to create the perfect suspension feel for your riding style.