How To Check Tyre Pressure: A Beginner's Guide

Emily Hanson 7 minutes Published: 26/08/2021

Rory feels like he's always tanking his car up with fuel. It guzzles petrol as quickly as he downs a pint at his local on a Saturday night. He bought this car because it was supposed to have excellent MPG. What's the deal? Well, Rory doesn't know it, but his uneven tyre tread wear is wreaking havoc.

Beth's just been in for her MOT and out she came with a big fat fail. She’s fuming. She needs her car to get to work. Why did she fail? Her tyres aren't up to scratch. They all need replaced as soon as possible. She only replaced them a few months ago, so she has no idea what’s worn them down so dramatically.

Graeme is driving along the motorway, laughing with his friends. Out of nowhere, his car pulls sharply. It collapses on one side, leaving them to spiral out of control. When it grinds to a halt, Graeme and his friends are left in a state of panic, hearts racing and breathless. What the hell just happened? Graeme has just had a tyre blowout.

What do these three drivers have in common? None of them regularly check their tyre pressure. Rory's car is struggling to motor along when his tyres have such uneven contact with the road, so it's using a hell of a lot more fuel than is normal. Beth's tyre tread was below the 1.6mm minimum for similar reasons to Rory. Graeme's wheels gave up because they were well under-inflated. Do you know another thing they probably have in common? None of them even know how to check tyre pressure.

Many of us don't remember to check our tyre pressure until we're due our MOT and we have a casual flick through an MOT checklist. Then we're all frantically looking for an air pump and pressure gauge. We shouldn't be leaving such an important task to the last minute like this!

In this blog, we're going to talk you through why we need to check our tyre pressure regularly, when to do it, how to check it, and how to fix it!

What is tyre pressure?

Your car tyre pressure is basically a measurement of the amount of air that is circulating around the inner lining of your tyre. It's measured in two ways, depending on whether you're an imperial or metric kind of guy/gal.

The two measurements used are:

  • Pounds per square inch (PSI), one for imperial fans.
  • Bar, a metric measurement that is the equivalent of 14.5ish PSI.

During development and testing, your vehicle manufacturer will determine how much pressure should be in your wheels, accounting for different weight loads.

Why should I check my tyre pressure?

The entire weight of your car is supported by its wheels, so these wheels need to be strong enough to carry the load. To be sturdy enough for the job, they need to be filled with the right amount of air until they reached the prescribed air pressure reading. Your tyres automatically lose a bit of air from them every month, around 2 PSI every 4 weeks, so you need to keep an eye on them to make sure they're ship shape.

Your car tyre pressure directly impacts how well you can navigate corners and brake in your car, which is essential not only for everyday driving but in emergencies too. Under-inflated tyres don't come into contact with the road evenly, causing them to wear excessively on the inside and outside edges of the tyre tread and also increasing your stopping distances due to poor road grip. Over-inflated tyres have a smaller contact area with the road which also causes poor braking distances and uneven wear.

If your tyre pressure is off, it can really rack up your repairs and maintenance bill. Since your tyres are becoming worn rapidly, you'll need to replace them more frequently. They also can't do their job properly so your car has to try extra hard to push along the road, increasing fuel consumption, reducing your fuel efficiency and pushing up the price at the petrol pump.

Checking your tyre pressure regularly shouldn't just be seen as a suggestion - it should be seen as a necessity. If you want to protect yourself and others on the road and keep your maintenance and fuel costs low, read on.

When should I check my tyre pressure?

The recommended frequency for checking your tyre pressure varies a lot from source to source. Some say weekly. Some say every time you drive. We think you should check monthly at the very least, and definitely more often if you regularly take long journeys or rack up a lot of miles in the average week.

You might notice a warning light flashing up on your dashboard from time to time too. Since 2012, all new cars sold in the EU have to be fitted with a Tyre Pressure Monitoring System (TPMS) which signals to you when your tyre pressure is too high or too low. If you see this, check your pressure readings pronto.

In hotter weather, your tyre pressure decreases more rapidly, so be aware of this in the summer months and adjust your pressure checking schedule accordingly.

How to check tyre pressure

It's a little bit on the finicky side but your tyre pressure check isn't too difficult. You don't need to take it the local mechanic on a monthly basis to do it for you. Just follow these steps and you'll be good as gold:

  1. Wait until your car is cool. It shouldn't have been driven in the last three hours. The heat can affect the pressure reading on the car.
  2. Put the handbrake on and make sure that the ignition is off.
  3. Get your hands on a tyre pressure gauge. You might have one at home or you can use one at a petrol station. Before you start, make sure it has been calibrated properly. If you're not sure about the one at the petrol station, ask a forecourt attendant to give you a hand.
  4. Work out what the ideal pressure is for your car and its weight load. You can find this information in the owner's manual or in the inside ledge of the driver's door. In this ledge, there should be a sticker which sets out the correct tyre pressure, accounting for different weight loadings i.e. for 2 people or 4 people, so on. You can also use this tyre pressure finder.
  5. Take the dust cap off of the tyre valve. Place it somewhere safe, but don't put it on the ground. It might get dirty and then you'll not be able to get it screwed back on.
  6. Insert the pressure gauge into the stem. Press down on the valve stem and check for an accurate reading. Compare it to the requirements set out in the vehicle handbook. Make sure you're comparing like for like, so if your requirements are set out in imperial, read the imperial measurement on the gauge.
  7. If it's too inflated, deflate it. If it's under-inflated, inflate it (check the next section for more info on how to do this properly).
  8. Remember to check all four of your wheels and your spare wheel so it's always good to go when you need it.

How do I fix my tyre pressure?

There's a simple fix for both over and under-inflated tyres.

If your tyre is over-inflated, you can release air by pulling the pump nozzle away from the tyre valve. Hissing air will escape. Don't go crazy here though - do it in bursts and regularly check the reading until it's at the correct pressure.

If you have an under-inflation problem, inflating your wheels is easy. Remove the pressure gauge, grab an air pump and attach it to the tyre valve. Pump in a little air at a time and pop the pressure gauge back in at regular intervals to check how your readings are doing.

To make sure that your tyre pressure stays pretty consistent for longer you can take these steps:

  • Check your tyre tread is 1.6mm.
  • Don't load the car with a ton of extra weight if you don't need to.
  • If you do need to carry extra weight, make sure your wheels are inflated with an adequate amount of pressure.
  • And generally just be a safe, sensible driver on the road!

Tyre Pressure Check - Check

By making sure that you have the correct tyre pressure, you're making sure that you're not shelling out wads of cash on fuel unnecessarily and you're shielding yourself from MOT failures and accidents.

With just a few simple steps that you can do yourself at home or at your local petrol station, you can check your tyres are properly puffed up with air and ready to hit the roads!

Other Maintenance Tips

If you're ticking off items on your car maintenance checklist, we're here to help. We've got a bunch of guides for keeping your car running in good working order, like how to check your brake pads! Check out these car maintenance tips from the experts and consider downloading some of these car maintenance apps!