Tyre pressures for a full load, a holiday or towing

Most cars have two sets of tyre pressures: one for everyday driving and a higher set for when the car is carrying a lot of weight. Plenty of drivers never use the second set. Here's when you should, how to read the label, and what changes when you hitch up a caravan or trailer.

Why there are two sets of figures

It's the air in a tyre that carries the weight of the car. Add a full load of passengers and luggage and the tyres squash further, the sidewalls flex more, and flexing makes heat. The higher pressure lets the tyres carry the extra weight. TyreSafe says most car makers give two recommended pressures, one for lighter loads and one for a laden car, and that it's important to switch between them. Here's what running too soft or too hard does.

How to read the label

The label is usually on the driver's door pillar, sometimes inside the fuel flap, and the same figures are in the handbook. Layouts vary between makes, but most have:

• A row for each tyre size. Find the size that's on your car. It's on the tyre's sidewall: here's how to read it.
• Separate front and rear figures. They're often different, so set each pair to its own figure.
• A normal column and a full load column. The normal figures may be marked with a number of people, such as "1 to 3 people". The higher set says "full load" or "max load", or shows a loaded car.
• Sometimes an "ECO" figure as well. The handbook will explain when that applies.

Figures are given in bar or kPa as well as psi. 1 bar is 100 kPa, or about 14.5 psi. When you check your car's pressures by registration here, our results page has a "Fully loaded" switch wherever the data for your car includes laden figures, so you can see both sets.

When to use the fully loaded figures

• A full car, with every seat taken, especially on a long trip.
• Holiday luggage: a packed boot, a loaded roof box, or bikes on a rack.
• Heavy loads, like building materials or a run to the tip.
• Towing a caravan or trailer.

Heavy load, a hot day and motorway speed together are when a soft tyre is most likely to fail, so a loaded holiday trip is exactly when the right figures matter. If you're not sure what counts as a full load for your car, the handbook usually explains.

Towing: the car's tyres

A caravan or trailer pushes down on the tow ball, which puts extra weight on the car's rear axle. Check your handbook first: many tell you exactly what to do. Nissan's, for example, says to inflate the tyres to the full-load cold pressure on the label whenever you tow.

Where the handbook doesn't say, TyreSafe advises setting the car's rear tyres to the fully laden pressure. If the full load figure is the same as normal, it suggests adding 4 to 7 psi (0.3 to 0.5 bar) to the rear tyres instead. Whatever you do, never go above the maximum pressure moulded on the tyre's sidewall.

Towing: the caravan or trailer's tyres

A caravan or trailer has its own pressures, and they're not the ones on your car's label. TyreSafe says caravan tyres often need higher pressures than the same tyres on a car because they carry more weight, and the Caravan and Motorhome Club mentions tyres that need 50 psi or more. You'll find the figures in the caravan's handbook, and sometimes on a plate inside the caravan or marked on the wheel arch. For a trailer, check its handbook or the tyre maker's load and pressure tables.

• Check them cold before every trip, and the spare too.
• Check their age. Caravans spend a lot of time parked, and a tyre can look fine and still be too old. The Caravan and Motorhome Club recommends replacing caravan tyres at five years old and never using them past seven. For tyres that need 50 psi or more, it says to check them for deterioration from three years and stop using them at five. Age counts from when the tyre was made, not when it was fitted: here's how to find a tyre's age.

Nose weight and payload, briefly

• Nose weight is how hard the hitch presses down on the tow ball. The Camping and Caravanning Club says it's normally between 50kg and 100kg, and it shouldn't exceed the limit for your car's tow ball or the caravan's own limit. You can measure it with a nose weight gauge.
• Loading the caravan or trailer. The Highway Code says to spread the weight evenly, with heavy items over the axle, and make sure there's a downward load on the tow ball.
• Weight limits. Your car's maximum weight is in the handbook and normally on a plate or sticker on the car. Passengers, luggage and the load on the tow ball all add to what the car is carrying. A caravan mustn't go over the maximum weight on its own weight plate.

After the trip

Once you've unloaded, set the tyres back to the normal figures, checked cold. The higher ones are for carrying extra weight; the normal ones are what the car is set up for day to day. If your car has an indirect warning system, with no sensors in the wheels, reset it after each change. Here's how to reset the warning on your make.

Changing pressures for a load takes five minutes with a gauge and a pump. It's worth doing every time you pack the car for a big trip.