PSI for car tyres explained

The first practical pneumatic tyre was invented by a Scottish vet called John Boyd Dunlop in 1887. Two years earlier, German engineer Karl Friedrich Benz produced the first practical motor car. In the earliest days of motoring, if your car had rubber tyres they were solid.

Dunlop saw that by making the tyre a rubber tube and filling it with air, you got a better ride and lower rolling resistance. It was the bicycle industry that first exploited this and pneumatic-tyred bikes were soon winning races. Early car makers soon followed.

What is PSI?

To find the correct tyre pressures for your car, you can look in the vehicle handbook, or for convenience, there is usually a sticker somewhere on the driver’s door frame or in the fuel filler compartment. You may also see a PSI figure printed on the tyre’s sidewall, but ignore this, it’s simply the maximum pressure the tyre can handle.
Most makers give tyre pressures in bars (one bar is equivalent to 14.5 PSI) but there’s no need to convert as most tyre pumps and garage air lines now show both standards, so you can simply set the bar pressure.
You will always see two pressures quoted, one for normal use and one for heavy loads. If you are going on holiday with all the family and their luggage, you should use the higher pressure. Note also that pressures aren’t always the same all round; you may find that there’s a difference between the recommended pressures at the front and rear, so check carefully.

Still unsure?
Why not get a professional to take a look? Protyre offer Free Tyre Checks at all of our garages within our expanding UK network. Our expert technicians will inspect your tyres for tread depth level, tyre pressure, wear and damage to make sure they are safe and legal. If your tyres need replacing, they will offer sound, impartial advice on the best tyres for your vehicle. Click the button below to book:

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Why pressures are important

It is important to keep your tyres at the right pressure. Too low and you will create extra resistance that will increase fuel consumption. Low pressures will also make the steering feel heavier. Too high and you will create uneven wear as the centre of the tread will wear out faster than the edges, you will also make the ride harder. Handling and safety are affected either way.
It’s important to note that when your tyres are hot, after a long run for example, the pressure is higher by as much as four to six PSI, because the air in them expands. You should always set your tyre pressures when the tyres are reasonably cold to ensure accuracy.
It really is worth checking your tyre pressures regularly because various events such as hitting a pot hole or clipping a kerb can cause a drop in pressure. Modern cars now have pressure monitoring systems fitted, but it’s still wise to check yourself as these often only trigger when there is quite a substantial pressure drop. Checking your tyres regularly can also give you early warning of other problems such as slow punctures, damaged sidewalls or worn tread before they become a major issue.
If you are unsure if there’s a problem, at Protyre our qualified fitters are always happy to carry out a free tyre check for you. With garages around the UK, there will be a location somewhere near you and you can book an appointment online.
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If you need replacement tyres, we stock many leading brands including Falken, Sumitomo and Bridgestone, so we have something to meet all needs and all budgets. Protyre can also provide expert servicing and MOTs.

About the author

David Sholicar

David is the National Retail Operations Manager for Protyre. One of David’s areas of responsibility and expertise is dealing with the DVSA and MOT’s for Protyre. As the Authorised Examiner Designate Manager ( AEDM ) David deals with applications for changes to the many Vehicle Testing Stations ( VTS’s) including managing the growth of the Number of MOT testing stations that Protyre operate, allocating MOT tester roles, and monitoring the MOT Test logs to ensure that Protyre MOT standards are maintained as the best in the industry. David handles the relationships with our parts suppliers to ensure that Protyre only fit the best quality servicing parts, brake parts, and other aftermarket quality parts at the right price. David is also involved in ensuring that all technicians are trained or assessed to carry out the work completed in all centres, and that Protyre has a robust Quality control ( QC) Procedure in all centres. David is also involved in developing the customer service standards and customer service training for all Protyre team members to ensure that all Protyre customers can expect the highest levels of customer service. At Protyre we believe we have the highest levels of customer service excellence that can be found, not only in the garage industry, but also when compared to other retail organisations. Another area of expertise is David’s involvement in developing Protyre Operational, Environmental, and safe working procedures. David has worked for some of the UK’s best retailers and this expertise has been a key component in helping develop Protyre into a highly respected company within the fast fit industry. David’s mission is ensuring that Protyre is the local garage that you can trust.

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