Tyre pressure is not only vital to your safety on the road, it also helps your tyres last longer and can improve your vehicles fuel efficiency, ultimately saving you money twice over.
It is therefore crucial that you ensure your tyres are always properly inflated by checking them at least once a month and always ahead of a long journey.
Ensuring your tyres are properly inflated is a relatively straightforward process and you don’t need a motor mechanic qualification to be able to do it yourself.
Our comprehensive guide explains everything you need to know and gives step-by-step instructions on how to check your tyre pressure.
What is tyre pressure?
Tyre pressure is the measurement of the volume of air inside the tyre when it is inflated. Formerly measured in pounds per square inch (psi), it is now usually expressed in bar (1 bar = 14.5038 psi).
Pressure will gradually reduce over time and especially during warmer weather, therefore regular checking and topping-up is necessary to maintain the vehicle manufacturer’s recommended pressure.
The two key words here are safety and efficiency. A properly inflated tyre will provide longer life, quicker steering response, better fuel efficiency and a smoother ride than an incorrectly inflated tyre. Both under-inflation and over-inflation can cause problems, including premature tread wear and possible tyre failure.
Benefits of properly inflated tyres
The benefits of properly inflated tyres are:
• Optimised vehicle performance
• Improved handling
• Enhanced safety
• Increased fuel efficiency
• Longer tyre life span
• Reduced CO2 emissions
How to check your tyre pressure
Maintaining proper tyre inflation is relatively simple and essential to the overall performance of your vehicle. It is therefore strongly recommended you check your tyre pressure at least once a month. Just follow these steps:
Check the manufacturer’s recommended psi
You will find this in your owner’s manual; on the driver’s side door jamb or on the inside of the fuel tank cap.
The plate will feature a lot more information than you might expect, that is why it is a good idea to check your details before you set off to check your tyre pressure, particularly if you are doing it for the first time.
There will be different pressures for different tyre sizes; the front and rear tyres and also the weight of the load you will be carrying (eg if you are going on holiday and your car is fully loaded with passengers, suitcases, hand luggage, bikes, etc). This is why it is a good idea to jot the numbers down.
These are examples of the tyre pressure information plate found on a Mini Cooper D. The label clearly denotes the tyre size and front and rear tyre pressures in bar. It also identifies the required pressure if the car is fully loaded with passengers and luggage:
What to do if the numbers are in bar and not psi?
This can be a bit confusing at first, put don’t panic. You just need to convert them into a psi reading in order to use some gauges and air compressors. Use our tyre pressure converter chart to quickly change from one to another.
You can do this is one of two ways:
1. Go online and search ‘convert (your requirement) bar to psi’
The conversion will appear as something like this:
2.60 bar = 37.7098 psi
Don’t bother rounding the figure up or down, just take the first two numbers
2. Alternatively, you can calculate the conversion yourself. Basically, 1 bar = 14.5038 psi and the formula for conversion is:
14.5038 x bar
Eg: 2.6 bar = 37.7098 psi
What equipment do I need?
To check your tyre pressure you will need a tyre pressure gauge or use of a gauge on the inflation equipment found at most garages and petrol stations.
Your tyre pressure gauge can be digital or standard and you can also purchase a portable air compressor to adjust the levels, which run from your car battery or 12v power port. The gauge and air compressor found on most fuel station forecourts are often free, but some have a nominal charge of 50p to £1.
Make sure your tyres are cold
This is where having your own gauge can come in handy, but if you have to use one at a fuel station make sure it is close by. Tyres are deemed cold when the vehicle has been parked for at least three hours or driven less than a mile at a moderate speed.
Check and adjust the pressure
Make sure you read the instructions on the gauge and air compressor before you get started, especially if you have to insert a coin and want to get your money’s worth. Also ensure you have parked your vehicle so it is within reach of the equipment, hose, etc.
How to test and adjust the tyre pressure
Once you are ready, remove the dust cap from the valve on the first tyre and place the pressure gauge on the valve stem, press down hard enough so the hiss sound disappears and the gauge provides a reading. With a standard gauge, the air pressure will push a small bar out from the bottom of the gauge. Measurement units are etched into the bar. A digital gauge will display the reading on a screen.
Adjust the pressure accordingly on each tyre using an air pump. Don’t worry if you over fill the tyres, because you can always let some air back out.
Do not over-inflate your tyres
It is very important not to leave your tyres over-inflated to a greater pressure than the maximum that is indicated on the sidewall of the tyre. And you certainly should never drive on over-inflated tyres, because they can result in decreased traction and poorer breaking distances. Over-inflated tyres have a smaller contact patch with the road, which means it will get more use and therefore wear out quicker. Premature wear adds up to a shorter life span and the need to replace the tyre sooner than if it were correctly inflated.
Repeat every month
Now you know how easy it is to check your tyre pressure it is important to make it part of your regular motor maintenance routine. Do it at once a month in order to improve vehicle safety, maintain fuel efficiency and extend tyre life.
Spotting the signs of incorrectly inflated tyres
Unfortunately, you can’t always tell at a glance or by kicking them if your tyres are properly inflated, unless they are seriously deflated! However, you don’t have to be a trained mechanic to spot the signs that they have suffered as a result of being driven on with incorrect air pressure for some time. Under-inflated tyres will exhibit excessive wear on the inside and outside edges of the tread. Whereas over-inflated tyres will wear unevenly across the central part of the tyre.
Environmentally friendly tyres
Finally, it is worth pointing out that properly inflated tyres are also miles more eco-friendly. It all comes down to rolling resistance. Tyres that are low on air pressure have greater rolling resistance. That means your car’s engine works harder, using more fuel and increasing CO2 emissions.
So for such a relatively simple piece of vehicle maintenance, checking your tyre pressure can deliver enhanced safety, better performance, big savings on fuel and replacements and finally, lower your carbon footprint! That’s a lot of benefits for a couple of minutes work.
Denna Bowman, Head Office