As the four bits of your car that are actually in contact with the road, your tyres are incredibly important.
And like most things, your tyres need a bit of love and care to keep them working at their best. In this car maintenance article, I’ll talk through how to check your tyre pressures to keep them perfectly inflated. Let’s get started.
Why check your tyre pressures?
Look, I know that checking your tyre pressures isn’t the most exhilarating task in the world but not doing so can be costly and dangerous. However, since it's something even a DIY car maintenance novice can do, there's simply no excuse not to check.
An under inflated tyre will sag onto the road, increasing the contact between the tyre and road. This increases friction, which costs you money, and can lead to the early failure of the tyre because the tyre is not in the correct shape.
An over inflated tyre pushes the centre of the tyre out, decreasing the contact between tyre and road. This, in turn, reduces the amount of grip you have and increases the likelihood of the early failure of the tyre because all the load is on a much smaller area of the rubber.
Under and over inflation is such a serious problem in the UK that the law sets quite strict guidelines in place. In the UK, tyres must:
- be inflated as to be fit for the purpose for use to which vehicle is being put (your manual will have the recommended inflation for your vehicle)
If you don’t inflate your tyres correctly, you could be hit with a fine of £2,500 per tyre and receive three points on your license!
What pressure should your tyres be?
The first step to checking your tyres is finding out what the correct pressure is for each tyre. This information is usually printed in a couple of different locations. The most common ones are:
- Your car manual
- Your car door sill
- Inside your petrol cap
While your car manual is a great resource, it usually covers every trim for the model, which means there are pages and pages of recommended tyre pressures. This makes it pretty tricky to find the correct tyre pressures for your particular car. I usually check the petrol cap and door sill first as they will give you the pressures for your actual car. If the stickers are missing or it's raining, I'll try the manual.
Also watch out if your car has had different tyres fitted too as they may require different pressures.
Three options for checking your tyre pressure
Now you know what the correct tyre pressures are, it’s time to actually check them.
In this section, I’ve included the three most common ways of checking tyre pressure: TPMS, handheld gauges and air pumps. I know that there are more ways to check tyre pressure but we’d be here all day if I discussed them all.
(If you think I’ve missed anything particularly important, leave a comment and I’ll add your suggestion to the article.)
Option #1 — Tyre Pressure Monitoring System
All new vehicles sold in the EU must have a Tyre Pressure Monitoring System (TPMS). TPMS is an automatic system that constantly monitors the pressure of your tyres and alerts the driver if the pressure either increases or decreases too much.
Since TPMS provides automatic and immediate feedback, drivers know straight away when their tyre pressures aren’t right and can stop at the next petrol station to add (or release) some air. If you’re leasing, your car will probably be brand new so it should have TPMS installed.
Option #2 — Handheld Gauge
Handheld gauges range from simple analogue dials to fancy Bluetooth-enabled gauges that hook up to your smartphone. Regardless of how complex they are, most will work in the same way. (As a quick caveat, we always recommend you refer to the device manual for instructions. Tyres are under a great deal of pressure so it’s important to use your gauge as intended.)
First, make sure your tyres are cool. Hot tyres will have hot gases inside them and this will give you an abnormally high reading.
Second, unscrew the valve cap and put it somewhere safe.
Third, attach the gauge to the tyre valve and push down firmly. The gauge should now give you a pressure reading. Once you’ve got the reading, unattach the gauge and screw the valve cap back on.
Option #3 — Air Pump
An air pump (usually located at petrol stations or motorway services) works in, more or less, the same way as a handheld gauge but with a couple of slight tweaks.
First, find out if the pump has a setting that allows you to check the tyre pressure. Some will and some won’t. If the pump doesn’t have a pressure check setting, set it to the recommended pressure of your tyres.
Second, make sure your tyres are cool then unscrew the valve caps and place them somewhere safe.
Third, pull the hose over to the tyre and attach the nozzle to the valve.
If the pump has a pressure check option, it will display the current pressure on the screen. If it doesn’t have a pressure check option, the pump will start inflating the tyre to the pressure you typed in earlier. While it is inflating the tyre, the current pressure will display on the screen.
How often should you check your tyre pressure?
Although modern tyres form a very tight seal, some air will leak out over time — usually around 1 psi or 0.07 bar per month — so it’s important to regularly check your tyres.
As a general rule, I’d recommend checking your tyre pressures once a month. And when you’re checking your pressures, it’s also a good idea to inspect the general condition of the tyre.
Obviously, if you notice a tyre looking a little flat or feel your steering is a little heavier than usual, you shouldn’t wait until your monthly pressure check.