Fox 40 setup
The 40 has four dials and a lot of travel, so start from known numbers. Put in your weight for your starting numbers, straight from Fox’s own charts.
Pump to 64–76 psi, then measure sag and adjust.
Compression, spacers and limits
- Compression: 5 clicks out high-speed, 10 clicks out low-speed, counted from fully closed.
- Rebound: Turn the dial fully clockwise until it stops, then count the clicks back out.
- Volume spacers at 203 mm: ships with 2, max 5.
- Max pressure 120 psi.
- Source: FOX 2025 40mm owner’s manual (tech.ridefox.com/bike/owners-manuals/2980) — banded ranges
Fix what you feel
Tap what your fork does. Fixes are for your GRIP X2. Change one thing at a time, then ride the same section again.
Harsh over roots and braking bumps
Too much air, too much high-speed compression, or rebound too slow.
- Check sag first. Under 15% means too much air.
- Open high-speed compression 2 clicks (counter-clockwise).
- Only harsh on back-to-back hits? Open low-speed rebound 1 click.
Dives under braking and on steep roll-ins
Not enough low-speed compression, or too much sag.
- Add low-speed compression 2 clicks (clockwise).
- Still diving and sag is past 20%? Add 2–3 psi.
Bottoms out hard on drops and big landings
Not enough high-speed compression, or the air spring isn’t ramping up enough.
- Add high-speed compression 1–2 clicks. Still bottoming? Add one volume spacer.
- Stay within Fox’s max spacer count: 5 on 203 mm, 7 on 190 mm.
Never uses full travel, even on big hits
Too many spacers, too much air, or too much compression.
- If sag is right, remove one volume spacer.
- Open high-speed compression 1–2 clicks.
Bouncy, or clunks at full extension
Rebound is too fast.
- Add low-speed rebound 1–2 clicks (clockwise). If it kicks after big hits, add 1 click of high-speed rebound.
Rides lower and lower through rough sections
Rebound is too slow, so the fork packs down.
- Open low-speed rebound 2 clicks. If it packs on fast hits in a row, open high-speed rebound 1 click.
Tell Suspend how it felt and it gives you the exact click to change on your Fox 40. Free for your first bike.
Full Fox 40 reference
For the 2025-and-newer 40 with GRIP X2. Fox’s 2025, 2026 and 2027 manuals print the same pressure, rebound and spacer numbers, and its 2024 manual (GRIP2 era) has them too. Fox’s product page describes a revised GRIP X2 and a Glidecore air spring on the newest 40, but its manual has not changed, so these are Fox’s published numbers. Older 40s have their own manual on tech.ridefox.com.
Fox 40 air pressure chart
| lb | kg | psi |
|---|---|---|
| under 150 | under 68 | 52–64 |
| 150–180 | 68–82 | 64–76 |
| 180–210 | 82–95 | 76–87 |
| 210–250 | 95–113 | 87–101 |
psi. Source: FOX 2025 40mm owner’s manual (tech.ridefox.com/bike/owners-manuals/2980) — banded ranges.
Fox 40 rebound clicks by weight
| lb | GRIP X2 low | GRIP X2 high |
|---|---|---|
| under 130 | 10 | 10 |
| 130–140 | 9 | 9 |
| 140–150 | 8 | 8 |
| 150–160 | 8 | 8 |
| 160–170 | 7 | 7 |
| 170–180 | 7 | 7 |
| 180–190 | 6 | 6 |
| 190–200 | 5 | 5 |
| 200–210 | 5 | 5 |
| 210–220 | 4 | 4 |
| 220–230 | 3 | 3 |
| 230–240 | 3 | 3 |
| 240–250 | 2 | 2 |
Turn the dial fully clockwise until it stops, then count the clicks back out. Push the fork down hard and let go. If it clunks at full extension, rebound is too fast.
Fox 40 sag in millimetres
| Travel | 15% (firm) | 20% (plush) |
|---|---|---|
| 190 mm | 28.5 mm | 38 mm |
| 203 mm | 30 mm | 41 mm |
Measure with the compression adjusters fully open, dressed to ride, weight spread across saddle, bars and pedals.
Fox 40 compression settings
| Damper | Start at |
|---|---|
| GRIP X2 | 5 clicks out high-speed, 10 clicks out low-speed, counted from fully closed. |
Fox 40 volume spacers
| Travel | Ships with | Max |
|---|---|---|
| 203 mm | 2 | 5 |
| 190 mm | 3 | 7 |
Spacers change how hard the fork ramps up at the end of its travel, not its sag. Add one if you bottom out too easily, remove one if you never get near full travel.
Which Fox 40 damper do I have?
- GRIP X2: Two dials on top of the right leg (a high-speed ring around a low-speed dial) and two stacked at the bottom.
The 40 comes as a Factory fork with GRIP X2, in 190 and 203 mm travel.
Fox 40 service interval
Fox recommends a full service every 125 hours of riding or once a year, whichever comes first. Fox says to service more often if you ride lift-accessed downhill or park.
Questions
What air pressure should I run in my Fox 40?
Fox gives a range per weight band. A 170–180 lb rider is in the 150–180 lb band: 64–76 psi. Start in the middle, around 70 psi, then set sag to 15–20%. Never go over 120 psi.
How much sag should a Fox 40 have?
15–20% of travel: 30–41 mm on a 203 mm fork, 28.5–38 mm on a 190 mm fork. Measure with the low-speed compression fully open, dressed to ride, with your weight spread across saddle, bars and pedals.
How many clicks of rebound on a Fox 40?
It depends on your weight. From fully closed, a 170–180 lb rider starts at 7 clicks out on low-speed rebound and 7 on high-speed. Lighter riders run more clicks out.
Does this work for my older Fox 40?
For the 2024-and-newer 40, yes: Fox’s manuals for those years print the same chart. Older 40s have their own chart in their year’s manual on tech.ridefox.com.
Related guides
Sources · last checked 2026-10-09
Starting points from the manufacturer’s charts, not a substitute for your fork’s manual. Always confirm with a sag measurement and stay under the max pressure.