What tyre pressure for sand, gravel and rock

If you make one change when the bitumen ends, make it this one. Dropping tyre pressures does more for traction, comfort and component life than any accessory you can bolt on, and it costs nothing but the time to air back up.

The principle is simple. A tyre at lower pressure deforms more, which lengthens the contact patch, which spreads the vehicle's weight over more ground and lets the tread conform to what it is driving over. On sand that means flotation instead of digging. On rock it means the tyre wraps the obstacle instead of skating off it. On corrugations it means the tyre absorbs the ripple instead of transmitting it into the vehicle.

Rough starting points

These are starting points for a mid-weight four-wheel drive, not prescriptions. Your correct pressure depends on vehicle weight, tyre construction and load, and the only way to find it is to start conservative and work down.

Note the last row, because it is the one that catches people. Rock is the exception to "lower is better". A soft tyre on sharp rock pinches the sidewall against the rim and cuts it. On genuinely sharp country you want pressure closer to road settings, not further from it.

What low pressure costs you

Airing down is a trade, not a free win.

• Rim deseating. Too low, combined with a sharp steering input or a side load, and the bead can unseat. That turns a manageable situation into a recovery.
• Sidewall damage. A bulging sidewall is exposed. Rocks and stumps that would have bounced off now catch it.
• Heat. A deformed tyre flexes, flexing generates heat, and heat destroys tyres. This is why you must air back up before returning to the highway, not when you next remember.
• Steering feel. The vehicle will feel vague and will roll more in a corner. Slow down accordingly.

The technique that goes with it

Low pressure buys flotation. Momentum keeps it.

In sand, the aim is steady progress in a gear that keeps the engine pulling without wheelspin. Sharp acceleration digs. Sharp braking builds a wall of sand in front of the tyre. Steering inputs should be gentle and early, because at low pressure the tyre takes a moment to respond and abrupt inputs are what unseat beads.

If you are losing momentum, the answer is almost never more throttle. It is usually less pressure, a straighter line, or backing out and taking a run at it in your own tracks.

Airing back up

Carry a compressor. This is not optional equipment on any trip where you intend to air down, because the alternative is driving to the nearest servo on soft tyres and destroying them on the way.

A decent twin-cylinder compressor will bring a set of four back to road pressure in a reasonable time. A cheap single-cylinder unit will do it too, slowly and hot, and will need rest periods. Buy for duty cycle rather than headline flow rate.

A quality gauge matters more than people expect. The one built into most compressors reads optimistically, and being ten percent out at the bottom of the range is a much bigger proportional error than at the top.

Buy the gauge and the deflator at the same time as the compressor, and check they thread onto the valve stems you actually have. Mismatched fittings are the most common reason a kit gets left in the drawer.

Where this applies

The surface-by-surface detail sits in the pieces that go with it: beach driving for tides and salt, recovery boards for when pressure alone is not enough, and all-terrain versus mud-terrain tyres for why tread pattern matters far less than pressure does.

The rule that matters most

Air up before you hit the bitumen. Every time.

Heat is cumulative and highway speed on a soft tyre builds it fast. The failure mode is not a slow leak, it is a sidewall letting go at a hundred kilometres an hour with a loaded vehicle. This is the single most preventable serious incident in touring, and it is preventable by stopping for ten minutes.