Road bike tire pressure calculator

How road tyre pressure is calculated

Road tyres used to be pumped as hard as they would go. Today most riders run wider tyres at lower pressures, because a tyre that absorbs small bumps rolls faster and grips better on real roads. This calculator is one of the free LeCoach cycling calculators, fixed to road tyres from 23 to 35 mm.

It starts with a base pressure for each width at a total system weight of 80 kg, on smooth tarmac, tubeless and dry: 85 psi for 25 mm, 74 psi for 28 mm, 62 psi for 32 mm. The base scales in a straight line with your weight. The front then goes 4 % lower and the rear 4 % higher, because the rear wheel carries more of your weight.

Road tyre pressure by rider weight and width

Smooth tarmac, tubeless, dry, 8 kg bike. Each cell shows front / rear in psi, with bar in brackets. Cells marked * exceed the 72.5 psi hookless limit on at least one wheel.

Going from 25 to 28 mm drops pressure by about 9 to 14 psi for the same rider. And a 90 kg rider on 30 mm tyres needs about the same pressure as a 70 kg rider on 25 mm.

Hookless rims and the 72.5 psi limit

Many modern carbon road wheels use hookless rims: the rim wall has no hook, so the tyre is held by its tight bead and the air pressure inside. Under the ETRTO standard, which ISO 5775 follows, tubeless tyres on hookless road rims are limited to 5 bar, or 72.5 psi, front and rear, whatever you weigh.

At the default 84 kg on 28 mm tyres, both wheels hit the cap. As a rough guide:

• About 60 kg: 28 mm tyres stay under the limit.
• About 70 kg: 30 mm is the narrowest width that fits.
• About 80 kg: you need 32 mm.
• About 90 kg: 32 mm still puts the rear at 79 psi; 35 mm brings it to 64 / 69 psi (4.4 / 4.8 bar).

Switch on "Hookless rims" and the calculator caps both pressures and tells you when it does. If the cap keeps kicking in, choose a wider tyre. Also check that your tyre is approved by its maker for hookless rims.

Rough tarmac, cobbles and wet roads

Choosing "Rough tarmac or cobbles" lowers pressure by 8 %, so the tyre soaks up chipped surfaces and cobbles instead of bouncing off them. For the example rider on 28 mm tyres that is 69 / 74 psi (4.8 / 5.1 bar). Add "Wet conditions" for another 5 % less: 65 / 71 psi (4.5 / 4.9 bar).

More pressure is not automatically faster. Above a certain point the tyre stops absorbing vibration, so you and the bike bounce instead. On a typical lane the fastest pressure is lower than most riders expect. Planning a long sportive on poor roads? The gran fondo training plan covers the fitness side.

Tubes or tubeless on a road bike

• Tubeless is the baseline. With no tube to pinch, you can run lower pressures, and sealant fixes most small punctures.
• Inner tubes add 6 % to protect against pinch flats: 79 / 86 psi (5.4 / 5.9 bar) for the example rider on 28 mm.
• Narrow tyres with tubes need the most air. On 23 mm with tubes, the same rider needs 102 / 110 psi (7.0 / 7.6 bar), one reason so many riders have moved to 28 mm.

Common mistakes on the road

• Running 100 psi out of habit. On 25 mm or wider tyres, most riders need far less.
• Ignoring the hookless limit. Overinflating a hookless rim risks the tyre coming off.
• Entering the printed width. On wide rims tyres measure wider; use the measured width.
• Going below 50 psi. The calculator will not suggest less, because road tyres turn vague and pinch more easily below that.

When to change your road pressure

• Winter roads: choose the rough surface.
• Moving to wider tyres: re-enter the width. Above 35 mm, use the gravel bike tire pressure calculator.
• Worn tyres: see when to replace bike tires before a big event.

The bike tire pressure calculator covers all bikes, and the cycling speed calculator shows what your power gives on the road. Ask LeCoach how to pace your next sportive or road race and it answers from your own power data and FTP.