Tyre Pressure: Understanding BAR and PSI

Proper tyre pressure is essential for safe and efficient driving, but many people are unsure of the differences between BAR and PSI.

To properly look after and maintain your car tyres, it is important to understand tyre pressure and the different ways in which you can measure the pressure.

What is tyre pressure?

Tyre pressure refers to the amount of air inside a tyre, measured in pounds per square inch (PSI) or BAR.

In our recent tyre pressure guide, we covered why maintaining the correct pressure - as specified by the vehicle manufacturer - is important as tyres with the incorrect levels can have such issues as:

• Reduced fuel efficiency.
• Increased risk of tyre damage or punctures.
• Compromised handling and braking performance.

Checking and adjusting tyre pressure regularly is a simple but essential maintenance task that can improve your safety on the road and extend the life of your tyres.

What is the difference between BAR and PSI?

BAR and PSI are both units of measurement used to express the air pressure inside of a vehicle's tyre.

BAR is the metric unit, whilst PSI is the imperial unit of pressure - most commonly used in the United States.

One BAR equates to roughly 14.50 PSI – so for example a tyre with a pressure of 2 BAR has a pressure of approximately 29 PSI.

While both units serve the same purpose, there are some key differences. BAR is measured in increments of 0.1, which provides greater precision when measuring tyre pressure.

PSI, however, is measured in increments of 1.0 and so if thought of by some to be more intuitive and therefore easier to use.

Is BAR or PSI better?

As with most things, that's up for debate. Some argue that BAR's precision makes it superior, while others gravitate towards the simplicity of PSI. Ultimately though, it comes down to personal preference. Or how you’ve been shown to do it in the past.

Regardless of which you use, make sure to check often – ideally once a month and before and long car journeys.

This is because regular checks and proper maintenance will help to prevent an increase in the rolling resistance of a tyre, overt tyre wear, and also a poor performance.

BAR to PSI conversion table

Below we have created a quick conversion table that shows the corresponding values between BAR and PSI for some common tyre pressures:

To convert BAR to PSI, simply multiply the BAR measurement by 14.5. To convert PSI to BAR, divide the PSI measurement by 14.5.

Understanding tyre pressure recommendations

Knowing where to find the recommended tyre pressure for your vehicle – whether you have EV tyres or standard tyres - is crucial for maintaining optimal performance and safety.

Each vehicle manufacturer designs and builds their models with a recommended tyre pressure. Often working closely with tyre manufacturers. By maintaining this, you are using the vehicle in the exact way it was intended.

The performance of the steering, rolling resistance and the braking capabilities of the car all rely on the tyres meeting a set pressure.

If you are unsure what the tyre pressure should be for your vehicle, there are generally 2 easy ways to find out. Most will include the numbers in the vehicle handbook.

They also include a sticker on either the inside door of the driver or passenger side.

It’s also worth noting that the tyre pressure requirements may alter depending on whether a vehicle is laden or not.

If you have a lot of luggage or heavy items in your car, a manufacturer will typically recommend a higher tyre pressure that if not.

Please always check your vehicle’s tyre pressure requirements and if you are unsure speak to an expert – such as the manufacturer themselves or a local tyre fitting centre.

What PSI should my tyre be?

The recommended PSI for your tyre will depend on several factors. It is crucial that you consult the vehicle's handbook or the tyre pressure sticker located on the door jamb. This will tell you the specific PSI for your car - normally a standard and vehicle-laden version.

Following this information correctly ensures optimal performance, safety, and fuel efficiency of your vehicle.

Common misconceptions about tyre pressure

There are several common misconceptions about tyre pressure, including the following:

1. Higher air pressure will result in better performance and fuel efficiency. However, this is not the case. Overinflated tyres can lead to uneven wear, a harsher ride, and reduced traction. Always use the manufacturer recommended pressure.
2. Colder weather doesn’t influence the tyre’s air pressure. Although it can be minimal, the level of pressure can decrease in cold weathers. This means that during colder months, you may need to check this a bit more than normal - and adjust accordingly.
3. Tyres don't need to be checked if they look fine. Although a tyre may look good – i.e not flat – it’s still extremely important to regularly test the pressure levels. When you are checking the tyre pressure, it is also a good time to give them condition a visual check. Looking for any bumps, cuts or foreign objects stuck in the tread.

Importance of correct tyre pressure

So, as we have seen, regularly ensuring that your vehicle’s tyres contain the recommended pressure is a very important part of vehicle maintenance. One that you can do yourself with very little fuss.

Regardless of whether you prefer to use BAR or PSI you can always find the correct pressure for your vehicle and almost all gauges will display both.

TL;DR - To ensure safe and efficient driving, it is important to understand tyre pressure (whether that’s using BAR or PSI – two sides of the same coin), and regularly maintain the recommended pressure for your vehicle.