Mountain bike tire pressure calculator

How MTB tyre pressure is calculated

Mountain bike tyres work at a fraction of road pressures. The tyre is your first piece of suspension: it wraps around roots and rocks for grip, while still supporting you in corners and protecting the rim on hard hits. This calculator is one of the free LeCoach cycling calculators, set up for 2.2 to 2.6 inch MTB tyres.

The method starts from a base pressure for each width at a total system weight of 80 kg, on flow trails, tubeless, trail casing: 24 psi for a 2.4 inch (61 mm) tyre. It scales in a straight line with your weight, adjusts for trail, casing and inserts, then drops the front 6 % and raises the rear 6 %.

MTB tyre pressure by rider weight and trail

2.4 inch tyres, trail casing, tubeless, no inserts, dry, 14 kg bike. Each cell shows front / rear in psi, with bar in brackets.

The trail setting lowers pressure by 5 % for roots and mixed terrain and 10 % for rocky, technical ground.

Tyre width, casing and inserts

Width. For the same 94 kg system on mixed trails with a trail casing:

Casing is how thick and stiff the sidewalls are. A light XC casing folds more easily, so it needs 4 % more air: 26 / 30 psi in the example. A tough enduro or DH casing supports itself, so it runs 4 % less: 24 / 27 psi.

Inserts. A foam insert protects the rim and supports the sidewall, so the calculator takes off another 5 %: 24 / 27 psi with a trail casing. Combine an enduro casing, inserts and rocky trails and the same rider is at 22 / 25 psi (1.5 / 1.7 bar).

Why the front and rear gap is bigger on a mountain bike

On a road bike the calculator splits front and rear by 4 % each way; on a mountain bike, 6 %. In the example the rear ends up 3 psi above the front. Two reasons:

• The front steers and does most of the braking. On loose ground it washes out first, so it gains most from extra grip.
• The rear takes the hardest hits. On drops and square edges your weight lands on the rear wheel.

Rim strikes, burping and how to tell you are too low

Too low shows up in three ways:

• Rim strikes. A loud ping or a hard thud on rocks and roots means the tyre has bottomed out. Repeated strikes can dent the rim or cut the tyre.
• Burping. In a hard corner or on a heavy landing, the tyre rolls on the rim and spits air or sealant past the bead.
• Squirm. The bike feels vague and the tyre folds when you lean into berms.

If you notice any of these, add 1 psi at a time. The calculator never suggests less than 16 psi. Tyres that bounce, skip and lose grip on roots mean the opposite: go 1 psi lower.

Common MTB pressure mistakes

• Copying road thinking. A harder MTB tyre is rarely faster on a trail; it just grips less.
• Using one pressure for every trail. A dry flow trail and a wet, rooty descent need different numbers.
• Running tubes at tubeless pressures. Tubes pinch-flat easily off-road. The calculator adds 6 % for tubes: 27 / 30 psi (1.9 / 2.1 bar) in the example.
• Ignoring casing. A light XC tyre at enduro pressure folds in corners.

When to change your MTB pressure

• Wet or muddy trails: switch on "Wet conditions" for 5 % less.
• New tyres, casing or inserts: re-enter them.
• Bike park or uplift days: hard landings call for rim protection. Fit a tougher casing or inserts rather than only dropping pressure.
• Worn tyres and brakes: see when to replace bike tires and when to replace brake pads.

For 35 to 50 mm tyres, use the gravel bike tire pressure calculator; for all bikes, the bike tire pressure calculator. For fitness, see the mountain bike training plan. LeCoach builds your training plan around your goals and suggests changes, with the reason, when your recovery data calls for it.