Ensuring you have the correct tyre pressures can have an impact on how your car handles, its fuel economy, and, most importantly, your safety. Regularly checking your tyres is an easy way of ensuring you’re keeping to the right pressures, but how do you do it? Let us talk you through it step by step.
What is Tyre Pressure?
Tyre pressure is a measurement of the amount of air that is inside your tyres, and is measured in pounds per square inch (PSI), or BAR pressure. 1 bar is equal to approximately 14.50377psi, so will always be at a much lower figure than psi.
Why Should I Check My Tyre Pressure?
Driving with the wrong tyre pressures can result in a change in your stopping distance or increase your chances of suffering a tyre blow-out.
- Driving with under-inflated tyres:
- Your tyres will flex more and get hotter, meaning a blow-out is more likely.
- Your stopping distance will increase and you will have poorer handling, meaning an accident is more likely
- The edges of your tyre tread will wear quicker
- The rolling resistance will increase, meaning you will be running with a higher fuel consumption
- Driving with over-inflated tyres:
- The centre of your tyre tread will wear faster
- Your contact area with the road is reduced, resulting in a lack of traction
- Increased stopping distances
- Your ride will be more uncomfortable due to less flex in the tyres (although don’t under-inflate for a softer ride, as this is just as dangerous, as outlined above)
What Should my Tyre Pressure be?
Recommended tyre pressures vary from car to car, so make sure you check your vehicle handbook to let you know exactly what pressure you need for your tyres. Alternatively most cars will have a small sticker denoting which pressures you need, usually located inside the fuel hatch or on the drivers’ door edge.
The figures stated in these will be figures for cold tyres, i.e. ones that haven’t been driving around for at least two hours, so always make sure to check them before a long journey. There are usually two figures quoted, one for a “normal” load and one for cars carrying particularly heavy weights.
If you still can’t find the correct pressures, a quick check online for your car’s manufacturer customer service should be able to answer your question, otherwise websites such as Halfords or Kwik Fit offer a system where you can input your number plate to receive your required pressures.
When Should Tyre Pressure be Checked
Tyre pressures should only be checked when the tyres are cold – this means they haven’t been driven for a couple of hours. This is because the pressure will increase as they heat up, and if you set your temperatures to the recommended setting while they are warm, the pressure will likely be too low.
If you are checking your pressures at a petrol station, try to make sure it’s at the start of your journey and only a very short drive away to ensure your tyres don’t heat up too much.
How to Check Tyre Pressure
Checking your tyres is one of the easiest pieces of car maintenance you can do, and most petrol stations or garages will have specific tyre pressure pumps for use for this very task. They are often coin operated, so it’s always worth having a little loose change handy.
- Check your recommended pressure. Before you start any work on checking your pressures, make sure you have the recommended figures to hand so you can get a quick answer to whether you’re over or under inflated. If using a system at a petrol station, you can then input this figure into the pump so it measures exactly what you’re looking for.
- Remove the dust caps. Every wheel will have a dust cap covering the valve. For speed it’s a good idea to remove all four at once, but make sure you keep them somewhere safe while carrying it out so they can be reinstalled.
- Check the pressure of the tyre. Simply press the pressure gauge on to the valve until a hissing sound stops and you receive your reading.
- Let out any excess air. If your tyres are over-inflated, press the metal pin in the valve stem down to let air out.
- Refill with air. If any tyres are under-inflated, press the air compressor (which is the same as the gauge if using a petrol station system) down onto the valve stem until the right PSI is shown on the gauge. Most petrol station systems will beep at you once at the correct pressure.
How do Tyre Pressure Sensors Work
There are two types of tyre pressure sensor, either direct or indirect, and both will send a warning to your dashboard if the pressures are getting low/.
- Direct Tyre Pressure Monitoring System
- Direct TMPS is the most common system due to its reliability, and uses sensors that are located within the tyres themselves. The sensor sits to the back of the valve, where you apply new air, and can track the exact pressure within the tyre. When pressure drops, usually to around 25%, a warning light will appear on your dashboard and you should take your car straight to a petrol station to pump up the tyres. Some systems will even tell you which tyre needs checking.
- Indirect Tyre Pressure Monitoring System
- Indirect TMPS don’t have their own sensor and instead use another sensor that is located within the wheel, commonly the ABS sensor. These sensors track how the tyres are revolving, and underinflated tyres will have a smaller radius than tyres with correct pressures, so will make more – or irregular – turns. While it’s less accurate than a Direct TMPS, it still lets you know when you need to pump up your tyres.
The advantage of tyre pressure sensors is that you can get a quick warning to tyre pressures dropping, and if you notice that one is regularly dropping below what it should be at, you could be suffering from a slow puncture or leaking air from the trim – both of which should be checked by your local garage sooner rather than later.
When Would You Increase the Tyre Pressure?
A question that often comes up as part of your theory test, you would increase the amount of pressure in your tyres if you’re planning on carrying heavier loads than usual. The adjusted pressure will be listed in your vehicle’s handbook and you may also need to adjust your headlights accordingly.
For more hints and tips on keeping you and your car on the road, then visit our Car Care hub, where we guide you through everything from tyre pressures to brake fluid and lessons to your paperwork when selling a car.
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