Why it's vital to increase tyre pressure when carrying extra loads
Your tyres are the only part of the vehicle in contact with the road. That's why keeping your tyres in good condition and at the right pressure is essential for safe driving. In this article, we'll explain why both too much and too little pressure can be dangerous—and why tyre pressure needs to be carefully increased when your vehicle is fully loaded.
It's important to check your tyres regularly and maintain them at the recommended PSI. Even if your car is fitted with a tyre pressure monitoring system (TPMS), it's best to double-check the pressure with a gauge, just in case the TPMS is faulty.
When would you increase tyre pressure?
Imagine you're packing the car to head off on holiday. By the time the luggage has been stowed and the whole family have clicked their seatbelts, you've added a surprising amount to the vehicle's usual payload.
To calculate your car's maximum payload, simply subtract the kerb weight from the gross vehicle weight (GVW). Both are detailed in the manufacturer's handbook. If your kerb weight is 1000kg and the GVW is 1500kg, your maximum payload is 500kg. A full suitcase weighs up to 25 kilos. Include three or four people and it soon adds up—especially if you're also towing a caravan or trailer.
How does extra weight affect your tyres?
Under all that extra weight, loaded tyres behave as if they're underinflated. The right amount of extra tyre pressure is the solution, providing greater stability and enhancing fuel efficiency.
How much should I increase the tyre pressure?
What is the right loaded tyre pressure for you? This varies from model to model. You'll find your vehicle manufacturer's recommendation in the owner's manual. The information is also often listed on the inside of the driver's door and on the fuel cap. It's essential to be precise when topping up tyre pressure because even a heavily laden car can have dangerously overinflated tyres. For more information on this tricky topic, read our detailed article on what your tyre pressure should be.
Above all, don't forget to return your tyre pressure to its normal PSI value afterwards.
Why are overinflated tyres dangerous?
When your tyres are overinflated, it can significantly increase the risk of a blowout. Consider how dangerous this can be, especially when travelling at speed.
That's not the only risk of excessive tyre pressure, as you can read in our article about driving with overinflated tyres. Less of the tread is in contact with the road, reducing traction. As a driver, you'll experience a bouncier than usual ride with less responsive handling. This explains why adding tyre pressure when the vehicle is fully laden must be done carefully, in line with the manufacturer's guidelines..
FAQs
A faulty TPMS can result in an MOT fail, so it's important to check this beforehand. Read all about what’s checked in an MOT.
Yes, but carefully. You should pull over to check your tyres as soon as it's safe to do so. Get the full facts on what the tyre pressure warning light means, and how to reset it.
Overinflating your tyres "just in case" may seem tempting when your vehicle is carrying more weight than usual. In fact, it is potentially very dangerous. Blowouts are more likely and changes in braking and handling performance can compromise your safety. That's why, even when adding extra pressure to compensate for a heavier payload, it's vital to stay within the limits advised by the manufacturer.
Underinflated tyres will wear away at the edges and get damaged more quickly. That increases the likelihood of punctures. Low pressure also makes tyres heavier, which causes greater rolling resistance when driving. This can harm braking performance — increasing your stopping distance by up to four car lengths in wet conditions, with potentially fatal results. It can also increase fuel consumption — because the engine has to work harder to drive the wheels. As discussed above, carrying a lot of weight without correctly increasing the tyre pressure makes your tyres effectively underinflated.