Gravel Tyre Pressure: How to Find Your Optimal PSI
The short version: the right gravel pressure isn't the lowest — it's the optimal. Go too far under and you get slower and squirmier, not faster. Tyre width and surface move the number far more than your body weight does.
Tyre pressure is one of the cheapest performance upgrades on your bike — and on gravel it matters enormously. But the popular advice ("run it as low as you dare") is only half right. There's an optimal pressure, and dropping much below it makes you slower, not faster. Here's how to find it.
There's a sweet spot — and it's a real one
On smooth tarmac a firmer tyre rolls a touch faster, up to that surface's own breakpoint, because it flexes less. On gravel the breakpoint shifts substantially lower: a hard tyre bounces off every rock, wasting energy and losing grip. Dropping pressure lets the tyre conform to the surface and roll faster.
But only up to a point. Go too low and the casing flexes so much that casing losses climb back up — now you're slow and squirming through corners, striking the rim, and risking burps or pinch flats. Silca's research (which the model below is calibrated to) calls the turnaround the breakpoint. Your goal isn't the lowest pressure — it's to sit at or just below it. Being a little low is generally less costly than being equally high, but go too far under and the losses pile up fast. In short: lower than the sidewall max and lower than your road tyres — but probably firmer than the "run it super low" crowd suggests.
The levers that actually move the number
Not all inputs matter equally. Ranked by real-world impact:
- Tyre width — the biggest lever. A wider tyre holds far more air, so it runs much lower. Around 40 mm, every 2 mm wider drops roughly 3 psi. Measure your actual mounted width with calipers — it can differ from the printed size by several millimetres either way, depending on the rim.
- Surface — also big. Smoother and faster wants more pressure; rougher wants less. Moving one step rougher is worth roughly 4 psi.
- Tubeless vs tubes. Tubeless lets you run a touch lower (roughly 2–4 psi) because there's no inner tube to pinch.
- Your weight — weaker than you'd think. In Silca's breakpoint model, going from a 60 kg to a 110 kg system weight only adds about 4 psi — so don't over-correct for body weight.
- Front vs rear. The rear carries a little more, so it runs roughly 1–2 psi higher — not the 3–5 psi gap you'll often hear.
What counts as "typical gravel"?
The table below assumes "typical gravel." Surfaces vary enormously by region, so it helps to pin down the category — these match the steps Crux (and Silca) use, smoothest to roughest:
- Gravel 1 — smooth, fast hardpack dirt
- Gravel 2 — a typical, mixed gravel road (the table's basis)
- Gravel 3 — chunky, loose gravel
- Gravel 4 — rough, rocky, near off-road
Starting-point pressures
Computed for a 40 mm tubeless tyre on a typical (Gravel 2) road, with ~47% of weight on the front (Crux's gravel default). Starting points — then fine-tune. System weight = rider + bike + kit (roughly your body weight + 12–13 kg).
| System weight | Front (psi) | Rear (psi) |
|---|---|---|
| 60 kg (~132 lb) | 35 | 36 |
| 70 kg (~154 lb) | 36 | 38 |
| 80 kg (~176 lb) | 37 | 38 |
| 90 kg (~198 lb) | 38 | 39 |
| 100 kg (~220 lb) | 38 | 40 |
| 110 kg (~243 lb) | 39 | 41 |
Then adjust for the bigger levers:
- Tyre width: ±~3 psi for every 2 mm away from 40 mm (wider = lower).
- Surface: smooth hardpack (Gravel 1), +~4 psi; chunky/loose (Gravel 3), −~4 psi; rough and rocky (Gravel 4), −~7 psi.
- With tubes: start ~2–4 psi higher to cut pinch-flat risk.
Mind the limits. Never exceed the lower of your tyre's and rim's stated maximum pressure — this matters most with hookless rims, which have firm caps. And note that going tubeless removes inner-tube pinch flats but not casing cuts, burps, rim strikes or rim damage. If you're encountering burps or rim strikes, add a little pressure while remaining within component limits.
How to fine-tune by feel
Numbers get you to the trailhead; the trail does the rest:
- Start at the table value, then apply the width/surface/tube-setup adjustments.
- Ride a section you know well.
- Harsh, bouncy, poor grip? Drop 2 psi.
- Squirmy, tyre folding, rim striking, or burping? Add 2 psi.
- Repeat in 2-psi steps until it feels planted without bottoming out.
Signs you're too high
Harsh, fatiguing ride; the bike skitters off rocks instead of tracking; lost traction climbing or cornering on loose ground.
Signs you're too low (past the breakpoint)
Vague, squirmy handling; the tyre folds under hard cornering; rim strikes; burping air (tubeless) or pinch flats (tubes); and, counter-intuitively, you feel slower.
Tubeless: run lower, safely
Without a tube there's nothing to pinch between tyre and rim, so you can drop into the range where the grip and comfort gains live — a few psi lower (roughly 2–4) than the same setup with tubes, especially if the rim increases the tyre's measured width. If you ride gravel seriously and you're still on tubes, going tubeless is the single biggest pressure upgrade available — just remember it doesn't remove the risk of casing cuts, burps or rim strikes.
Frequently asked questions
What pressure should I run in 700×40c gravel tyres?
For a typical ~85 kg system on a normal gravel road, tubeless, about 37 front / 39 rear psi is a sensible starting point. Adjust for surface and feel from there — and never exceed your tyre or rim limits.
Should the front tyre be lower than the rear?
Slightly — roughly 1–2 psi. The rear carries a bit more weight; the small gap gives the front grip and steering feel without overdoing it.
Does rider weight change gravel pressure much?
Less than most people assume — in Silca's breakpoint model, only around 4 psi across a 50 kg range of system weight. Tyre width and surface move the number far more.
Is gravel pressure lower than road pressure?
Considerably — a road tyre might run 60–80 psi, while a typical gravel setup lives in the high-30s to low-40s, dropping further on wider tyres or rougher ground.
Tubes or tubeless for gravel?
Tubeless, if you can. It lets you run a few psi lower for more grip and comfort.
Sources & method
The PSI figures here are computed from Crux's tyre-pressure tool — a simplified model calibrated to Silca's Pro Tire Pressure Calculator and its breakpoint research. They're starting points for a healthy tyre and rim; your component pressure limits and your own testing always take precedence.
Let Crux dial it in
The exact number depends on your weight, measured tyre width, surface and tubeless setup all at once. Crux returns dialled-in front and rear PSI from a model calibrated to Silca's Pro Tire Pressure Calculator — alongside full ride analysis, gear tools and bike-service tracking, all on your iPhone. Private by design: your data never leaves your phone.
See Crux