The ultimate guide to understanding your tyre pressure

Written by Summit Tyres - May 2019


Your car tyres need to be inflated to the correct tyre pressure at all times to ensure safe and comfortable driving. But not everybody knows how to check their tyre pressure or understand what it means!

Checking your tyre pressure should be a quick and easy part of your car maintenance. As well as keeping you safe on the road, it can also save you both time and money!

It can often be confusing as to when and how often to check your tyre pressure, never mind understanding the amount of air to inflate your tyres with or how to know when it needs to be done. At Autocar, we want you to get the best out of your tyres, so we have combined our top tyre pressure tips in this guide so you can check your tyres with ease in the future.

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How do I check my tyre pressure?

There are 4 simple steps to checking your tyre pressure:

  1. Take a tyre pressure gauge and inflator (whether you have one of your own or head to your local garage/petrol station) and remove the tyre dust cap
  2. Attach the pressure gauge to the dust cap and record the result shown
  3. If the gauge shows less than your recommended pressure, inflate your tyres accordingly to the manufacturer’s recommended PSI or kPa. If your tyre is over the recommended pressure, you can adjust the gauge to release the air until it meets the recommend pressure
  4. Once the tyre has reached the correct pressure, secure the tyre dust cap back onto the tyre

Your tyre pressure can vary for many reasons. For example, if the weather is extremely warm, your tyre may expand and increase in pressure. This is the same if it is particularly cold outside; it is likely that your tyre pressure will lower in cold weather. It is important to keep this in mind if you decide to check your tyre pressure and inflate your tyres in the height of summer or winter.


What should my tyre pressure be?

The answer to this question depends on the car that you drive. Your tyre pressure differs depending on the make and model of your vehicle.

Depending on your car, you will easily be able to find your car manufacturer’s tyre pressure recommendation somewhere within the vehicle. Whether this is on the inside of the driver’s door, in the petrol or diesel or even located in the boot. Before you buy a car, it is best to ask the manufacturer where this is so you are not left searching when you go to check your tyre pressure.

No matter the tyre brand you decide to opt with, the tyre pressure measurement will be measured in the same quantity. In the UK, our tyre pressure is more often than not measured in Pound Per Square Inch (PSI) or sometimes Kilopascals (kPa) or Bar.


Are my tyres under inflated or over inflated?

It is possible for your tyres to be over or under inflated at any time. It is crucial to understand the difference between the two and how to get the perfectly inflated tyres as driving with either can be very dangerous.

A properly inflated tyre ensures that your car has balanced contact with the road as much as possible, ultimately making a journey safer and more efficient. If your tyres are balanced on the roads, this means they are less likely to be worn down at either side of the tyre, meaning that you can keep your tyres in better shape for longer.

Below we’ve highlighted the key signs and risks of having both under or over inflated tyres.

A diagram to show what a properly inflated car tyre looks like


Over inflated tyre signs and risks:

  • Loud tyre noise levels
  • Reduced tyre grip
  • Loss of traction
  • Worn damage in the centre of the tyre
  • Increased risk of tyre blow-out
  • Loss of traction and poor grip

Under inflated tyre signs and risks:

  • Vehicle handling becomes difficult for the driver
  • Worn damage at the edges of the tyre
  • Fuel consumption is increased
  • Road contact can be unbalanced and therefore dangerous
  • Decreased overall performance of the car


When should I check my tyre pressure?

The best time to check your tyre pressure is once every month and before you go for a long trip that requires a lot more driving than usual. Our Autocar experts recommend checking your overall car maintenance, as well as your tyre pressure, before long drives (whether you’re going on holiday or taking a trip to see family across the country). This is to ensure that there are not any unexpected troubles during your trip. It is also worth checking your tyres if you know your car is going to be experiencing different terrain to what it is used to.

We all fall into a habit of only checking our car when things start to sound, look or feel a little different than usual. If regular checks were made, these weird sounds or any damages would be less likely, saving you time and money.


What are tyre pressure sensors?

For some car manufacturers, they decided that checking your tyre pressure manually can often be missed on your car maintenance to-do list. So, as technology advanced over the years, some cars are now fitted with systems that monitor and warn you about the levels of your tyre pressure.

There are two types of tyre pressure sensors, direct TPMS and indirect TPMS.

Direct TPMS uses a sensor that is fitted onto each wheel of your car. This clever technology measures the tyres and is able to notify you with a light on your dashboard when your air pressure drops too low.

Indirect TPMS functions differently. It works with the Antilock-Braking System’s speed sensors which are also located on your wheels. If your tyre pressure falls below the manufacturer’s recommend amount, it ensure that the wheel speed rolls differently to your other tyres. A light on your dashboard will warn you if this has happened.

As well as understanding your tyre pressure, there are other important factors about your tyres that are handy to know such as understanding your tyre size and tyre labelling. When you own a car, it is your responsibility to care for it, both for your safety and your pockets too! For everything you need to know about your tyres, visit our help and advice page.


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