How to Set Suspension Sag: Fork & Shock Baseline
A clear, repeatable method to set fork and shock sag so your bike rides as intended. About 20–30 minutes at the workbench or in the garage.
Before You Start
Warning: Incorrect adjustment of suspension can cause loss of control and serious injury. If you aren't confident performing these procedures, take your bike to a qualified mechanic. This walkthrough covers why sag matters, how to measure it, and how to get baseline settings for both air and coil systems. Plan on about 20–30 minutes.
Why sag matters
Sag determines where your suspension sits in its travel when you're on the bike. Too little sag = harsh, skittish feel and poor traction. Too much sag = wallowy, imprecise handling and risk of bottoming out. Getting sag right is the biggest single setup step for handling and traction.
Tools & Supplies
Rubber O-ring or zip-tie sized for stanchion/shock shaft
Metric ruler or caliper (mm)
Shock pump (high-pressure, for air forks and rear shocks)
Small hand pump or shock-specific pump for coarse pressure changes
Allen keys / multi-tool (for seatpost or accessory adjustments)
Clean rag
Helmet and riding kit (to wear during measurement)
Steps: Set Sag for Fork and Shock
Note: Before you touch pressures or preload, clean stanchions and shock shafts so the O-ring slides freely.
1) Know your travel
Find total travel (in mm) for your fork and shock from the frame/fork spec or owner's manual. You'll use this to convert millimetres of sag into a percentage: sag% = (sag mm / total travel mm) × 100.
2) Prepare the bike and yourself
Place the bike on a level surface. Put on your usual ride kit (helmet, hydration pack, any tools you normally carry) — sag should be set with the load you'll actually ride with. Put the chain on the small chainring and stand the bike upright.
3) Install the O-ring/zip-tie and set the "fully extended" reference
Slide the rubber O-ring up against the dust seal on the fork stanchion and against the shock body eye or shaft seal for the rear shock. Compress the suspension fully by hand so the O-ring is at the top of the exposed shaft. This gives you the zero point.
4) Measure static sag (optional but useful)
Remove your weight and measure from a fixed bike reference to the O-ring position, or note the O-ring position relative to the dust seal. This tells you how much the bike settles under its own weight.
5) Sit on the bike and settle
Carefully mount the bike with your feet on the ground, sit in your normal riding position, and have a friend hold the bike vertical and steady. Bounce lightly a couple times and then stay still while the O-ring settles. Step off carefully.
6) Measure rider sag and calculate percentage
With the O-ring now lower on the stanchion/shaft, measure the displacement from the fully-extended reference. Convert to percent using the travel figure from step 1.
7) Adjust to target
Air fork or air shock: Increase pressure if sag is too large (bike too soft). Reduce pressure if sag is too small (bike too harsh). Make adjustments in small increments, then repeat steps 5–6. Use your shock pump — it provides the precision and range you need.
Coil spring: Increase preload if you need to reduce sag slightly, but preload only changes ride height, not spring rate. If the sag is far off, you likely need a different spring rate; consult a shop for spring sizing.
8) Finalize and recheck
Once you're in the target range, repeat the seating measurement 2–3 times to confirm consistency. Recheck after a short ride; occasionally the suspension will settle slightly and need a micro-adjust.
Gearhead Tip: Record the final pressures and settings for your typical kit and conditions. A simple note in your phone saves a lot of guesswork when weather or luggage changes.
Validation, Troubleshooting & When to Seek a Shop
Validation / What Good Looks Like
Use the formula sag% = (sag mm / travel mm) × 100 to confirm your result.
Aim to be within a few percent of your intended target and repeat measurements to remove variance from how you’re sitting.
Test on a short run: the bike should feel planted through rough sections, and you should avoid frequent bottom-outs.
Troubleshooting
Sag too high (bike feels wallowy): Add air pressure to fork/shock or, for coil, consider a stiffer spring.
Sag too low (bike feels harsh / skittish): Reduce air pressure or reduce preload. If you hit the lowest recommended pressure and sag is still low, you may have an incorrect spring rate.
Severe bottoming: Check rebound damping (too fast rebound lets the bike pack down) and consider added tokens or increasing pressure. If bottoming persists, consult your shock/fork manual or a shop.
Inconsistent readings: Ensure stanchions and seals are clean, and always use the same riding kit when measuring.
Gearhead Tip: If you switch tires, wheels, or add a framebag, recheck sag. Changes in rotating or carried mass change the baseline load.
When to Stop & Seek a Shop
If you suspect an incorrect spring rate (coil) — a pro can measure and recommend a swap.
If the damper feels sticky, rebound is inconsistent, or you hear unusual noises — suspension service is required.
After a crash, when you see play in bushings, shaft bends, or oil leaks — stop riding and have a technician inspect the unit.
Any internal damper or air can service (seal replacement, damper rebuild) should be done by a trained shop unless you have the manufacturer’s procedure and tools.
Before your next ride: verify axle/quick release or thru-axle torque, seatpost clamp, brake levers, and that suspension bolts and mounts are secure. Always do a low-speed test in a safe area.
Sources
Manufacturer setup guides (Fox, RockShox, Öhlins) — consult your unit's specific owner manual for exact procedures and limits.
Related Categories
Internal Links
Key Takeaways
Sag places your suspension in the correct portion of travel for traction and control.
Measure sag with an O-ring or zip-tie, convert mm to percent using total travel.
Adjust air pressure for air springs; adjust preload or change spring rate for coils.
Seek a shop for spring-rate selection, internal service, crash damage, or inconsistent damping.
FAQs
What percentage of travel should I aim for?
Target ranges depend on discipline and personal preference; many riders use a lower percentage for XC and a higher percentage for enduro or downhill. Use the formula sag% = (sag mm / travel mm) × 100 and tune from there.
Can I set sag alone and be done?
Sag is the baseline. After sag, you should tune rebound, low-speed compression, and pressure (or spring rate) to refine feel. A short test ride and small iterative changes are the fastest path to a dialed setup.
How often should I check sag?
Check sag after major setup changes (tires, wheels, pack weight), seasonally, or after suspension service. A quick check before a big ride is good practice.