Fox 38 160mm Grip X fork settings for a 100kg rider?

[mobeewales]

What is the ideal settings for a Fox 38 160mm grip x fork for a 100kg rider?

@Greg Watts

 

[Greg Watts]

At 100kg kitted up, here's a sensible baseline for a Fox 38 160mm GRIP X. Treat these as a starting point and tune from there — sag is the truth, the numbers just get you close.

Air pressure (spring)
Fox's own chart puts a ~100kg rider around 100–105 psi. For reference, Bear-uk logged 95psi giving 30mm sag at 87kg on a 38, so heavier means more — start at 100 psi and check sag.

Sag target
Aim for 15–18% sag (~24–29mm on 160mm travel). The 38 likes running firmer than you'd expect — @Ndanger found that letting sag drift toward 30mm brought on pedal strikes and vague climbing on his Cube; keeping it at 20mm or less sorted it. So if anything, err on the firm side.

Volume spacers (tokens)
GRIP X 38s typically ship with 1 token. At your weight, if you're blowing through travel on big hits, add a second before chasing more air pressure — keeps the early/mid stroke supple while ramping up the end. If you never use full travel, drop to a slightly softer spring and let a token do the support work.

Damping (GRIP X has HSC/LSC/HSR/LSR)
Start from Fox's recommended settings for your pressure, then:
• Rebound: heavier riders run faster rebound. Roughly LSR 5–7 clicks from closed, HSR 1–2 out. If the front packs down in successive hits, speed up; if it bucks back, slow down.
• Compression: start fully open on LSC and HSC and only add support if it dives under braking or feels wallowy. JC1982 ran his 38 at just 1 click of compression — most riders end up with very little.

Torque note
If you're popping the top cap to change tokens: it's a 32mm socket at 25Nm, not 40 — @steve_sordy flagged that over-torquing rounds off that low-profile alloy hex. Grease the cap to stop air leaks.

Set sag first, get rebound feeling controlled, then add compression only if you need it. Most setup faults at your weight are too little air and too much compression, in that order.

What bike's it going on, and what's it doing wrong at the moment — diving, harsh, or vague? Tell me that and I'll tighten these up for you.

 

[Powerslider]

I'm 200lbs (90 kg) and currently run my 2025 Fox 38 like this on my Levo 4:

• 2 volume tokens
• 101 psi
• LSR 4 (from closed)
• HSR 3 (from closed)
• LSC 8 (from open)
• HSC 1 (from open)

I'm pretty confident in my compression settings, but I'm just running the Fox suggested rebound settings.
Probably going to experiment bringing down the spring 1 or 2 psi next ride but I'm very, very close to where I want to be.

 

[Greg Watts]

I'm 200lbs (90 kg) and currently run my 2025 Fox 38 like this on my Levo 4: 2 volume tokens 101 psi LSR 4 (from closed) HSR 3 (from closed) LSC 8 (from open) HSC 1 (from open) I'm pretty confident in my compression settings, but I'm just running the Fox suggested rebound settings. Probably going to ...

Solid real-world data point - always useful when someone's actually dialled rather than just theorising.

Your LSC at 8 clicks from open is notably more compression than most riders run (the Fox baseline tends to be 3 - 5 out), but if it's working for you on the Levo 4 it's working - heavier bikes can genuinely ask for more support there, and Phoenix trails aren't exactly forgiving on loose-over-hard. If you ever feel it going harsh on successive chatter rather than just diving under braking, that'd be the first thing I'd back off.

On the rebound - LSR 4 / HSR 3 from closed is fairly slow for 90kg. Fox's suggested starting points tend to run conservative (i.e. on the slow side), which suits lighter riders but can cause packing down in repeated hits for heavier ones. Worth opening up LSR to 5 - 6 and seeing if the front feels more composed through repeated compressions rather than gradually riding lower. HSR 3 is reasonable; I'd leave that alone until you've played with LSR first.

On dropping 1 - 2 psi: at 101 psi you're already in a sensible range for your weight, but if sag is sitting under 15% it's worth the experiment. Just check sag before and after - that's the actual signal, not the number on the pump.

Two tokens at 90kg on a 160mm fork makes sense; keeps it from diving while preserving mid-stroke sensitivity. That bit sounds well sorted.

 

[Powerslider]

Solid real-world data point - always useful when someone's actually dialled rather than just theorising.

Your LSC at 8 clicks from open is notably more compression than most riders run (the Fox baseline tends to be 3 - 5 out), but if it's working for you on the Levo 4 it's working - heavier bikes can genuinely ask for more support there, and Phoenix trails aren't exactly forgiving on loose-over-hard. If you ever feel it going harsh on successive chatter rather than just diving under braking, that'd be the first thing I'd back off.

On the rebound - LSR 4 / HSR 3 from closed is fairly slow for 90kg. Fox's suggested starting points tend to run conservative (i.e. on the slow side), which suits lighter riders but can cause packing down in repeated hits for heavier ones. Worth opening up LSR to 5 - 6 and seeing if the front feels more composed through repeated compressions rather than gradually riding lower. HSR 3 is reasonable; I'd leave that alone until you've played with LSR first.

On dropping 1 - 2 psi: at 101 psi you're already in a sensible range for your weight, but if sag is sitting under 15% it's worth the experiment. Just check sag before and after - that's the actual signal, not the number on the pump.

Two tokens at 90kg on a 160mm fork makes sense; keeps it from diving while preserving mid-stroke sensitivity. That bit sounds well sorted.

I'll keep your LSC suggestion in mind.

For whatever reason I seem to like a bit more rebound damping. To me it quiets the bike and helps tracking.

On sag-I start with the prescribed sag, but then adjust to taste. I don't treat measured sag as law. The final arbiter is the ride experience instead of the tape measure.

All this being said-I'm a professional audio guy and not a professional suspension tuner. If I tell you how to adjust your audio system, you can take it to the bank. My suspension settings admittedly are just me sharing one average guy's setup.

 

[Greg Watts]

I'll keep your LSC suggestion in mind. For whatever reason I seem to like a bit more rebound damping. To me it quiets the bike and helps tracking. On sag-I start with the prescribed sag, but then adjust to taste. I don't treat measured sag as law. The final arbiter is the ride experience instead of ...

@Powerslider - all fair points, and honestly there's a lot of wisdom in "ride it, not the tape measure." Sag percentage is a useful starting point, not a commandment carved in stone.

On the slower rebound preference - that's a legitimate tuning choice, not a mistake. Some riders genuinely find it settles the front end and improves traction feel, particularly on looser terrain. Phoenix hardpack is probably less forgiving of a bouncy front than Peak District gloop, so your mileage - literally - will vary.

The audio analogy is a good one, actually. Suspension tuning is a lot like dialling a mix: the meters give you a baseline, but if it sounds right, it's right. You've put the time in, you know your trails, and you're close to where you want to be. That counts for more than any chart.