How to Set Up MTB Suspension

Get your riding weight

Weigh yourself wearing everything you ride in: shoes, helmet, hydration pack, knee pads, and any tools you carry. This is your system weight, and it is the number all pressure calculations are based on. A full hydration pack adds 2-3kg. Getting this number right matters more than any other single variable in suspension setup.

Open all damping adjusters

Before measuring sag, set every adjuster to its fully open position by turning counter-clockwise until it stops. On RockShox Charger 3 and 3.1 dampers, use the middle of range for compression adjusters rather than fully open. This ensures the suspension can settle freely into sag without being held up by damping resistance, which would give a false low reading.

Check service history

Stale oil makes settings inconsistent. RockShox recommends lower-leg service every 50 hours and a full damper rebuild every 200 hours. Fox recommends lower-leg service every 125 hours (less in wet or dusty conditions). If your suspension is overdue, service it before tuning.

Position the sag O-ring

Slide the rubber O-ring (or a zip tie) down against the dust wiper seal at the top of the fork lower leg. For rear shocks, push the O-ring against the seal at the top of the damper body. This is your reference point. It will stay wherever the suspension settles when you sit on the bike.

Set starting pressure and equalize

Use the suspension calculator or the sticker on the back of your fork lowers to find a starting pressure. Pump to that pressure, then remove the pump. Do not measure sag with the pump attached - the hose adds false volume to the reading.

RockShox Solo Air and DebonAir: After pumping, slowly compress the fork through at least 50% of travel five times to equalize the positive and negative air chambers. Do this after every pressure adjustment. Without equalization, sag readings will be inaccurate.

RockShox DebonAir+ (Pike C1, Lyrik D1, ZEB A2 and newer): The equalization dimple sits near 35% travel. Increase pressure in 50-75 PSI increments, cycle the fork 5 times through full travel after each increment, then repeat until you reach target pressure.

Fox FLOAT forks: No separate equalization procedure required. Pump to pressure, remove the pump, and measure sag.

Measure sag correctly

Lean your bike against a wall. Mount the bike fully kitted, get into your normal riding position with weight on pedals, elbows slightly bent, and hold that position for at least 10 seconds to let the suspension settle. Then step off carefully without bouncing or rocking the bike.

Measure the distance from the dust wiper to the O-ring. This is your sag in mm. Divide by total travel to get the percentage. Use the sag calculator to convert instantly.

Target sag by brand, spring, and riding style

Adjust pressure until you hit your target. After your first ride, check the O-ring. Ideally you want to use 90-100% of travel on the biggest hits without harsh bottom-out.

What rebound does

Rebound controls how quickly the suspension extends after compression. Too fast and the fork kicks back (pogo stick feel). Too slow and it packs down through successive bumps, never returning to full travel between hits, making the bike feel low and wooden.

Rebound dials are red on both Fox and RockShox. Clockwise (turtle icon) is slower. Counter-clockwise (hare icon) is faster. The correct setting is linked directly to air pressure: more pressure stores more energy in the spring, which needs more rebound damping (more clicks clockwise) to stay controlled.

Setting rebound from closed position

Turn the red rebound dial fully clockwise until it stops (fully closed / turtle icon). Then back it out counter-clockwise to the recommended number of clicks for your fork and pressure. Reference tables for Fox and RockShox are below.

Test: push the fork quickly to about 30% travel and release. It should return smoothly and settle without a second bounce. If it rebounds so fast it kicks your hands upward, add 1-2 clicks clockwise. If it feels sluggish and does not return fully before the next test, back off 1-2 clicks counter-clockwise.

Low-speed vs high-speed compression

Suspension speed here means the speed of the damper shaft, not the bike. Low-speed compression (LSC) handles slow inputs: rider weight shifts, nose-dive under braking, pumping through a berm, G-outs. High-speed compression (HSC) handles fast inputs: square-edge hits, rock gardens, drops and landings.

Many forks have only LSC as a blue lever or dial. High-end forks - Fox GRIP2, GRIP X2, RockShox Charger 3 RC2 - have both as separate adjusters. Simpler forks have a 3-position lever (Open / Medium / Firm).

Fox compression starting points

3-position lever: Start in Open. Move to Medium if the fork dives excessively under braking. Firm is for climbing only.

Fox GRIP2 and GRIP X (34, 36, 38): From fully closed (full clockwise), back out HSC 5 clicks and LSC 10 clicks. These are Fox official starting points from the 2025 owners manual at tech.ridefox.com. Add LSC 1 click at a time if the fork sits too low in its travel. Add HSC 1 click at a time if big hits feel harsh.

Fox GRIP X2 (38, 2024+): HSC 5 clicks from closed, LSC 10 clicks from closed. The X2 lets you tune LSC and HSC completely independently - use HSC for bottom-out control and LSC for ride-height support without affecting small-bump sensitivity.

RockShox compression starting points

Charger RC (Select, Base): Single LSC adjuster. Start at middle of range, not fully open. Add clicks if the fork wallows or dives too much. Back off if your hands sting over chatter.

Charger 3 RC2 and Charger 3.1 RC2 (Ultimate, Select+, Pike, Lyrik, ZEB): Has independent HSC and LSC. Start both at middle of their range - this is different from older RockShox dampers and is specifically recommended by SRAM for the Charger 3 system. Adjust LSC first, then use HSC only to control large impacts and bottom-out events.

What tokens and spacers do

Fox volume spacers and RockShox Bottomless Tokens sit inside the air chamber and reduce its volume. A smaller chamber means pressure ramps up more aggressively in the last third of travel, resisting bottom-out without affecting feel in the first half of the stroke.

This allows you to run a lower starting pressure for better small-bump sensitivity while still having strong bottom-out support. Adding a token improves bottom-out resistance. Removing a token makes the progression more linear and the end-stroke softer.

Fox volume spacer guide

Fork-specific spacer part numbers: Fox 32mm uses 8cc blue spacers (PN 234-04-811). Fox 34mm uses 10cc green spacers (PN 234-04-953). Fox 36mm uses 10cc orange spacers (PN 234-04-736). Fox 38mm uses 10cc yellow spacers (PN 234-44-189). Do not exceed the maximum spacer count listed in your fork owners manual.

RockShox Bottomless Token guide

Most RockShox forks ship with zero tokens. The Vivid Air rear shock often needs 1-2 tokens even at recommended pressure due to its larger air chamber. After adding a token, re-inflate to previous pressure and re-check sag. It will likely have risen slightly. Add 2-5 PSI and re-measure until you are back at your sag target.