Having the correct air pressure in your tyres is crucial primarily for road safety. Read on to find out why tyre pressures are so important and how you should adjust them.
It all depends on the load
What your tyre pressures are depends on the load you’re carrying. Think about a beach ball for a moment. If you weigh 80kg and sit on the ball, it will sink down a lot more than if your 30kg child sits on it. It’s a similar story with tyres. They will be squeezed much more if you’re carrying a family of five and all their luggage compared with if it’s you in the car on your own.
Why tyre pressures are important
Tyres are designed to be run with a certain amount of air pressure inside them. This pressure ensures the correct amount of tread is spread on the road. In turn, this has an impact on how well the tyre disperses water and how well the car sticks to the road in the wet. And it affects how quickly the car will stop when you brake heavily.
In addition, tyre pressure affects wear rate. A tyre that’s persistently under pressure will wear much quicker than one at the correct pressure. According to Michelin, every 0.5 bar (7psi) that a tyre is underinflated by will reduce its life by 5000 miles.
Lastly, tyre pressure influences fuel consumption. Tyres with too little air in them rub more against the road. This friction means the engine has to use more power to turn the wheels. That in turn uses more fuel. And if you’re going on holiday and covering a large number of miles, the extra fuel used by under-inflated tyres could have quite an impact on the family budget.
More load equals higher pressure
The heavier the weight inside the car, the more it will push the vehicle down onto the road. In turn, that puts more strain on the tyres. And it’s likely that when you head off on the family holiday, you’ll be carrying a heavier load than at pretty much any other time during the year.
Where to find the correct tyre pressures
First of all, check inside the fuel filler flap or on the door pillar (as in the Volvo, above). There is frequently a pictogram on one of these. It shows one pressure with three people inside the car, another set of pressures for five people plus their luggage.
If you’re going on holiday with all the family plus their luggage, you want to inflate your tyres to the higher set of pressures.
Look in the user manual if you can’t find the pictograms on the car. Should the manual be missing or the information not there, contact your car manufacturer’s help line.
How to check your tyre pressures
It’s important that tyres are cold when you check their pressure. Warm tyres will appear to have higher air pressure because air expands when it heats up. Check them when warm and you might think they’re OK when they’re actually under pressure. And always remember your car tyres might have different pressures front to back.
I’ve been writing about cars and motoring for more than 25 years. My career started on a long-departed classic car weekly magazine called AutoClassic. I’ve since pitched up at Autosport, Auto Express, the News of the World, Sunday Times and most recently the Daily Telegraph. When I’m not writing about cars and motoring, I’m probably doing some kind of sport or working in my garden.