What Tyre Width and Pressure for a Loaded Gravel Bike?

Width First

Pressure only makes sense once the tyre is wide enough, and most loaded riders are on tyres that are too narrow.

Surface	Width	Why
Smooth gravel, some tarmac	40 to 42 mm	Fast, adequate, the minimum for loaded riding
Mixed gravel, washboard	45 to 50 mm	The default for most bikepacking
Chunky, loose, embedded rock	50 mm and up	Where a wider tyre stops being optional
Anything with hike-a-bike	2.1 inch and up	You are on a mountain bike and should be

Loaded, a wider tyre is not a comfort upgrade. Extra weight increases the energy lost every time the wheel is deflected upward by a rock, and a wider tyre at lower pressure absorbs that deflection instead of transmitting it. On rough surfaces, wider is genuinely faster as well as more comfortable.

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The Starting Numbers

For a 45 mm tubeless tyre and a total system weight of about 90 kg, which is a 75 kg rider plus a 10 kg bike plus 5 kg of kit and water:

1.9 bar (28 psi) front, 2.1 bar (30 psi) rear.

Adjust by roughly 0.07 bar (1 psi) for every 2 kg the whole loaded system differs from 90 kg. Go up about 3 psi if you are running tubes, because you have no sealant and a pinch flat is now a possibility.

Go up for a 40 mm tyre and down for a 50 mm one, because the same deflection at a bigger air volume needs less pressure.

Weigh The Bike, Not Yourself

This is the part almost everyone gets wrong.

People set pressure by rider weight, then hang 8 kg of kit off the bike and ride the same numbers. On a 75 kg rider that is a 10 percent increase in what the tyres carry, and it lands disproportionately on the rear where the seatpack is.

So set your pressure loaded, with water in the bottles, the way you will actually ride. Or at minimum add 3 psi to the rear over your unloaded setting and accept that it is an approximation.

How To Find Your Number

Start at the figures above and go down in 2 psi steps over a few rides.

Stop when one of three things happens: you strike the rim on square-edged hits, the rear feels vague and squirms in corners, or you burp air when cornering hard. Then add 2 psi back. That is your pressure, and it is almost certainly lower than what you were running.

Do this once on the terrain you actually ride, not on a smooth road. The number that works on a fire road is wrong for embedded rock and the other way around.

The Thing That Undoes All Of This

Pressure drifts. Tubeless setups lose noticeably more than tubed ones, and a tyre you set on Friday is meaningfully softer by Sunday.

Check it every morning of a multi-day trip. That is the actual reason to carry a pump with a gauge rather than a bare mini-pump, and it is a thirty second job that keeps the numbers above meaning something for the whole trip.