The fox 36 fit 4 setup sits in a very specific place: supportive enough for aggressive trail riding, but simple enough that you can understand it without wrestling with endless dials. In this article I’m focusing on what the FIT4 damper changes in practice, how to set the fork up so it feels controlled rather than harsh, and where this older 36 still makes sense in 2026. If you are comparing a used fork, checking service parts, or just trying to get more from the one already on your bike, the details below will save time.
The fork only works as intended once the setup is right
- FIT4 is a three-position damper with Open, Medium and Firm modes, plus extra Open Mode Adjust on higher-spec forks.
- The most important setup targets are 15 to 20 percent sag and rebound matched to your air pressure.
- Fox’s current 36 lineup now lists GRIP, GRIP X and GRIP X2, so FIT4 belongs to an earlier generation of the fork.
- For UK trail riding, FIT4 works best when you want support, clean pedalling behaviour and predictable control on mixed terrain.
- If you are buying used, model year, travel, axle and brake standard matter just as much as the damper.
What the FIT4 damper actually changes
FIT4 is Fox’s older three-position trail damper, and that is exactly why it still interests riders: it gives you clear Open, Medium and Firm settings without the complexity of a full gravity-style cartridge. On Factory and Performance Elite versions, Fox added an Open Mode Adjust window with 22 extra clicks; I would start at 18 clicks out from fully closed, then tune from there rather than chasing the extremes on day one. In practice, that makes the fork easy to live with on mixed rides where you want a firm pedalling platform but still need proper descending control.
Fox’s current 36 page no longer lists FIT4 among the available dampers, which tells me this is best treated as an earlier-generation specification rather than the fork you would choose as a brand-new reference point. That does not make it obsolete. It simply means you should judge it as a proven used-bike or older-build option, not as Fox’s latest answer to all-mountain damping.
Once that is clear, the real question becomes how it behaves on the trail and how much setup it needs to shine.
How it feels on real trails
On the trail, FIT4 rewards a rider who wants a fork that feels organised. Open mode gives you the freedom to let the fork move on rough descents; Medium is the useful all-round setting for rolling terrain; Firm is there when the trail turns into a climb, a fireroad link, or a smooth sprint. I like that split because it keeps the fork’s personality predictable rather than vague.
- Open works best on roots, braking bumps, wet rock and any descent where front-wheel grip matters more than outright pedalling support.
- Medium is the mode I would expect to use most often on mixed British trail days, because it calms body movement without making the front end dead.
- Firm is for short climbs and smoother links, not for hiding a poor setup.
The setup basics that make the biggest difference
I would start every FIT4-equipped 36 the same way: set the fork to Open mode, put the correct air pressure in it, and then check sag before touching anything else. Fox recommends 15 to 20 percent sag for this fork family, which is the range that usually keeps the front end active without diving too deeply under braking. On a 2019 36 FLOAT, Fox lists a maximum pressure of 120 psi, or 8.3 bar, so there is room to tune, but not room to guess wildly.
| Rider weight | Starting pressure | Metric range |
|---|---|---|
| 120 to 150 lb | 55 to 63 psi | 54 to 68 kg, 3.8 to 4.4 bar |
| 150 to 180 lb | 67 to 76 psi | 68 to 82 kg, 4.6 to 5.2 bar |
| 180 to 210 lb | 80 to 89 psi | 82 to 95 kg, 5.5 to 6.1 bar |
| 210 to 250 lb | 93 to 106 psi | 95 to 113 kg, 6.4 to 7.3 bar |
Those are starting points, not a verdict. If you are running a lighter bike with a lot of front-wheel load, you may land a touch above the chart; if you prefer a more supple front end for slick roots and tighter corners, you may end up slightly below it. What matters is that sag lands in the 15 to 20 percent window and the fork still uses travel cleanly instead of crashing through it.
| Travel | 15 percent sag | 20 percent sag |
|---|---|---|
| 140 mm | 21 mm | 28 mm |
| 150 mm | 23 mm | 30 mm |
| 160 mm | 24 mm | 32 mm |
| 170 mm | 25 mm | 34 mm |
| 180 mm | 27 mm | 36 mm |
Once sag is right, rebound is the next lever that matters. A fork that returns too slowly feels packed down in repeated hits; one that rebounds too fast can top out and feel nervous. Fox’s own 36 chart puts FIT4 rebound at roughly 8 clicks out at 55 psi, 6 clicks at 75 psi, and around 4 clicks at 89 to 93 psi, which is a sensible place to begin before you fine-tune by feel.
If the fork still bottoms too easily after sag is correct, I would add a volume spacer rather than immediately adding lots of pressure. If it never gets near full travel, remove one. That one change usually tells you more about the air spring’s balance than three extra psi ever will.
That setup logic is what makes the fork feel properly sorted, and it also sets up the next part of the ride, which is how the modes should actually be used.
Open, medium and firm are not just a lockout
The easiest mistake with FIT4 is to treat it like an on-off switch. That misses the point. Open is your default for rough descending, Medium is the useful in-between mode for rolling trail and undulating climbs, and Firm is there for smooth climbing or quick sprints where you want the fork to sit higher. The fork feels best when you move between modes on purpose, not when you leave it in one place and hope the terrain will cooperate.
On higher-spec FIT4 versions, Open Mode Adjust adds another layer of control inside Open mode itself. Fox gives you 22 extra steps, with the larger number feeling plushest and the smaller number feeling firmer. I would start at 18 clicks out from fully closed, ride a familiar loop, and only then decide whether the fork needs a little more support or a little more compliance.
That approach matters on UK trails because conditions change quickly. A damp rooty climb can need Medium mode one minute and Open the next when the trail tips down. If you find yourself using Firm constantly just to keep the fork from bobbing, the setup is probably off somewhere else, usually air pressure or sag.
The next question is whether FIT4 is still the right benchmark against Fox’s newer 36 dampers.
How FIT4 compares with Fox’s current 36 dampers
Fox’s current 36 collection now centres on GRIP, GRIP X and GRIP X2, so if you are shopping in 2026, that is the comparison set I would use. FIT4 still makes sense on an existing bike, but it is no longer the new standard for the chassis. In practical terms, the newer dampers give you more modern tuning paths, especially if your riding has shifted toward harder hits and faster descents.
| Damper | Main character | Best use | What you give up |
|---|---|---|---|
| FIT4 | Supportive, straightforward 3-position control with optional Open Mode Adjust | Mixed trail riding, used bikes, riders who prefer simple logic | Less fine-tuning than Fox’s latest dampers |
| GRIP | Current 3-position trail option with easy setup | Riders who want simple adjustment and dependable climbing support | Not as gravity-focused as the higher-end options |
| GRIP X | Trail and all-mountain balance with an easy-access firm mode | Harder riding without jumping to a full enduro damper | More complex than FIT4, and not as aggressive as GRIP X2 |
| GRIP X2 | Most tunable and most downhill-focused | Fast, rough, technical riding where grip and support matter most | More adjustment to manage, and usually more fork than casual trail riders need |
If I were buying new, I would use that table to steer myself toward the current damper family rather than hunting for an exact FIT4 match. If I were buying used, though, I would care far more about condition, service history and chassis fit than about chasing the newest badge.
What I would check before buying one in 2026
If I were looking at a FIT4-equipped 36 today, I would check five things before money changed hands:
- Exact model year and chassis, because Fox’s 36 range changed over time and the current fork is not the same platform as the older FIT4 builds.
- Travel and brake standard, because older 36 forks used different brake mounts and some used floating axle systems, so rotor and hub compatibility matter.
- Remote type, because Push-to-Lock and Push-to-Unlock cable routing are not a casual swap; the topcap interface needs to match the fork.
- Service history, because a fork that moves smoothly on the stand and still feels tight on the trail is worth far more than a neglected one with a fancy spec sheet.
- Where and how you ride, because a fork used on wet, muddy, high-load trails needs more attention than one that only sees occasional dry-weather rides.
Fox still documents FIT4 cartridge rebuilds for 2019 to 2024 forks, so support has not disappeared, but that does not mean you should ignore condition. Fox also notes that suspension should be serviced more often when it is being worked hard or ridden in wet, muddy or dusty conditions, and if you hear, see or feel something unusual, the right move is to stop riding and have it checked.
For me, the smartest way to judge a FIT4-equipped 36 is simple: if the chassis fits your bike, the service history is clean, and the fork feels calm on your local trails, it is still a strong piece of suspension. If you want the latest Fox feel for a new build, look at the current GRIP family instead; if you already own the older fork, set it up properly and it can still ride very well.
