MTB and gravel tyre pressure: setting it for your weight and terrain

23 to 50 psi, or 1.6 to 3.4 bar. That is the range printed on the sidewall of a 29 × 2.40-inch mountain bike tyre, the Kryptotal Re, in Continental’s 2026/27 catalogue [1]. On paper, anything between those two figures will do. In practice, the right pressure depends mostly on you: your weight, the tyre’s width, how it is set up and the terrain of the day. Manufacturers’ charts give you a starting point, provided you know what they assume, because they do not all say the same thing.

What sets the pressure: weight, width and set-up

The ‘right’ pressure depends largely on the weight the tyre carries, Schwalbe points out: that of the rider and their luggage, with the bike itself counting for little [2]. The narrower the tyre and the heavier the load, the more air you need; a wide tyre makes do with less, and a tubelessWithout an inner tube: the tyre seals against the rim thanks to a liquid sealant, which also plugs small punctures. set-up can be run a little lower [2].

Inflating is a trade-off. Higher pressure cuts rolling resistance on the road, wear and the risk of punctures; lower pressure brings comfort and grip [2]. Kept too low for too long, it wears the tyre out early and cracks its sidewalls [2]. With an inner tube, it also exposes you to a pinch flatA puncture caused by an impact: the inner tube is pinched between the rim and an obstacle, leaving two small parallel cuts, hence its nickname, ‘snakebite’., and Michelin then advises raising the pressure [3]. A tubeless tyre, DT Swiss notes, can be run softer without the risk of pinching [4].

Then there is the question of which weight to enter in a chart, and here manufacturers do not agree. ENVE, the wheel maker, starts from the rider’s weight with all their kit, on a bike of average weight [5]. SILCA’s calculator, from the pump maker, asks for the total weight: rider, bike and luggage [6]. With an electric mountain bike, much heavier than a standard one, the gap between the two ways of counting widens. Before reading a chart, check what ‘weight’ means.

Mountain bikes: ENVE’s chart for a 2.4-inch tyre

ENVE publishes a chart broken down by weight, with front and rear given separately. Its figures assume a tubeless set-up; those reproduced here are for a 2.4-inch (61 mm) tyre on a rim with a 30 mm internal width [5]. The chart does not distinguish wheel diameter, 27.5 or 29 inches, which sometimes depends on the frame size.

Two caveats from ENVE change how you read it. Its rims have built-in pinch-flat protection, and its figures allow for that: on other wheels, you may need more air [5]. With a reinforced casing, double-ply or downhill, it suggests trying the bottom of the range instead [5]. And inner tubes? Its charts do not cover them. Among tyre makers, two simple rules: tubeless can be run a little lower, says Schwalbe, and a pinch flat is a sign you need more air, says Michelin [2, 3].

Gravel: three manufacturers, three answers

For gravelRiding on unpaved roads and tracks (gravel, dirt, forest roads) on a drop-bar bike with wide tyres, somewhere between road cycling and mountain biking., ENVE gives a single figure per row, with no split between front and rear, again for tubeless. Here are its figures for a rim with a 25 mm internal width [5].

SILCA’s calculator works differently. It looks for the fastest pressure on a given surface: the point beyond which impacts from the ground cost more energy than the tyre’s flexing [8]. So it asks for the total weight, the surface, the tyre’s measured width, the speed, the weight distribution and the type of casing [6].

Two surprises. Weight counts for little: from 70 to 110 kg, the pressure rises by only about 0.2 bar. And a butyl inner tube lowers the suggested figure rather than raising it. SILCA makes clear that its calculation aims at speed, not pinch-flat protection, and warns that a wide tyre on rough ground puts a standard inner tube at risk of pinching; the answer is then to go tubeless, or to pump it harder and give up a little efficiency [8].

Let’s do the sums for one rider: 77 kg with kit, a 10 kg bike, a 40 mm tubeless tyre. ENVE suggests 2.3 bar (34 psi) [5]. SILCA, on category 2 gravel and for 87 kg in total, 2.5 bar at the front and 2.6 bar at the rear (36 and 37.5 psi) [6]. Finally, the tyre maker WTB puts the best setting for a 40 mm gravel tyre at around 40 to 45 psi, or 2.8 to 3.1 bar, without giving a weight, and invites riders to adjust it to their style, terrain and weight [7]. Nearly 0.8 bar separates the lowest from the highest: each assumes a different rim, tyre and goal.

Dry, muddy, rocky or tarmac: fine-tuning for the terrain

Weight gives you the starting point; terrain does the fine-tuning. SILCA’s calculator shows it clearly: for 90 kg in total and a 40 mm tubeless tyre, the suggested pressure falls by nearly 1 bar between new tarmac and the roughest of its gravels, which SILCA describes as the worst surface in its calculator [6, 8].

On a mountain bike, Michelin notes that a very stony course may call for a different pressure, and that a higher pressure rolls better on kinder ground [3]. WTB gives the warning sign to watch for: if the tyre compresses all the way to the rim on big hits, or folds in corners, it needs more air [7]. On very grippy ground (loam, sandstone, tacky trails), ENVE adds that the top of its range may not be enough, and advises going up 5 to 10% at a time [5].

In mud or sand, the logic is reversed. Michelin observes that a lower pressure can help you keep moving on very loose ground [3], and SILCA admits that its own figure, 40 psi (2.8 bar) for a 33 mm cyclocross tyre on its worst gravel, would be far too high in a muddy race: grip is then what limits speed [8]. On tarmac, finally, a harder tyre rolls more easily, Schwalbe reminds us [2]: that is the first row of the table.

Front and rear: why the rear takes a little more

Sitting on the bike, you put more weight on the rear wheel. SILCA’s calculator assumes 47% of the weight at the front and 53% at the rear on a gravel bike, 46.5% and 53.5% on a mountain bike; from that it lowers the front pressure by 2.5 to 3% and raises the rear by 2 to 3% [6]. On a 40 mm gravel tyre, that comes to about 0.1 bar.

ENVE’s mountain bike chart points the same way, with up to 1 psi (0.07 bar) more at the rear [5]. Michelin advises always running the front of a mountain bike slightly softer, but generally using the same pressure in both wheels of a road bike [3]. For gravel, its guide does not say: ENVE’s chart gives a single figure, SILCA’s calculator two.

Bar and psi: converting and measuring accurately

ENVE’s, SILCA’s and WTB’s charts use psi, pounds per square inch; Schwalbe uses bar, and Continental’s catalogue psi. The conversion fits on one line, but the decimals soon trip you up: 2 bar is 29 psi, 2.5 bar 36.3 psi, 3 bar 43.5 psi.

You still need to read it accurately. The thumb test is not worth much: from about 2 bar, Schwalbe warns, every tyre feels fairly firm [2]. ENVE adds that pump gauges vary a great deal from one model to another, and that a valve core clogged with sealant skews the reading [5]. As for how often: at least once a month, according to Schwalbe, which considers a loss of about 1 bar a month normal, faster at high pressure [2]. With tubeless, WTB recommends checking every time you ride [7].

Enlarge photo

The ceilings: sidewall, rim and hookless rims

Charts give you a starting point; limits are not up for negotiation. The tyre’s sidewall carries a minimum and maximum: 34 to 72 psi (2.3 to 5.0 bar) for the 700 × 40 Terra Trail gravel tyre, 23 to 50 psi (1.6 to 3.4 bar) for the 29 × 2.40 Kryptotal Re [1]. The rim has its own maximum too, often lower: at ENVE, 60 psi (4.1 bar) for the G23 gravel rim with a 32 to 40 mm tyre, 40 psi (2.8 bar) for the G27 with a 42 to 50 mm tyre [5]. When the two differ, the lower one applies [9].

HooklessA rim whose edges lack the small lip that holds the tyre’s bead. The ETRTO calls it TSS, for Tubeless Straight Side. rims add a ceiling of their own. Schwalbe publishes the table, drawn up, it says, in accordance with the ETRTOEuropean Tyre and Rim Technical Organisation, which sets the dimension and usage standards for tyres and rims in Europe.: it falls as the tyre gets wider, and applies even if the sidewall promises more [10]. According to this table, a 40 mm gravel tyre must not exceed 3.5 bar (50.8 psi) on a hookless rim, even if its sidewall says 72 psi, and a 2.4-inch (61 mm) mountain bike tyre 2.5 bar (36.3 psi) [10].

SILCA’s calculator even displays a warning above 70 psi: in its view, a hookless rim should not be used above 72 psi [6]. That is, to within half a psi, the maximum the ETRTO and ISO set for a 28 mm road tyre on this type of rim, 5 bar or 72.5 psi, ENVE points out [11]. For a gravel or mountain bike tyre, the ceiling is much lower, as the diagram below shows.

Enlarge diagram

The rule to remember fits in one sentence: the chart gives you the starting point, the terrain adjusts it, and the lower of the tyre’s and the rim’s maximums is never crossed.

Worth watching

GMBN Tech goes through what tyre pressure changes on the trail, from traction, cornering and comfort to rider weight, terrain, tyre width and weather, to help you settle on your own figure.

The video is hosted by YouTube (Google): nothing loads until you play it, and Google may then set cookies.

Julien de Jurquet

Campervans, motorhomes, cycling and calculators

Julien de Jurquet writes for Outfarer about campervans, motorhomes, cycling and calculators. He reads instruction manuals to the very end and never lets a figure through without its unit, so that your choices rest on sums rather than promises.

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