Tag Archives | Tyre pressure
Cold weather tyre pressure
As you get behind the wheel this winter bear in mind that cold weather can affect the pressure in your tyres, and this makes driving in difficult conditions more hazardous. Your tyres feel the cold as much as you do, and when the temperature drops so does the pressure in your tyres. Similarly, if you drive somewhere with high altitude, your tyre pressure will drop faster. As a rule, with every 100C the temperature drops, your tyres lose between one and two pounds per square inch (PSI) or 0.07 to 0.14 bars. You should therefore check them more often during the winter months and it is recommended that you do this fortnightly. You’ll need to do this after your car has been parked for at least three hours as this will give you the correct cold tyre pressure, so don’t check them just after you’ve been driving. By making sure they are properly inflated, your car will have better traction on icy or wet roads. Even if you have a tyre pressure monitoring system in your car, you should still check your tyres. If you’re not sure what your car’s tyre pressure should be, you can find it on the door frame on the driver’s side, your vehicle handbook or on the fuel cap. Keeping your tyres at the correct pressure also helps with your fuel economy ensuring you get the full mileage from each litre of fuel.
Don’t be an aquaplaner
With frequent wet weather, it’s important to be aware of aquaplaning and how to handle it. Also known as hydroplaning, aquaplaning can happen if you’re driving on wet roads at speed. A layer of water builds up between your tyres and the road surface, making them lose contact with the road. As a result, you’ll have zero grip and be unable to steer or accelerate until you reach a drier section of road. Many modern driving aids, such as electronic stability controls systems, won’t help either once a car begins to aquaplane as these tools only work when your tyres are in proper contact with the road. To reduce your chances of aquaplaning, always keep your tyres inflated at the correct pressure and make sure the tread depth does not fall below the legal minimum of 1.6mm. This is important because the grooves in your tyres are designed to disperse water from beneath them. Aquaplaning happens when a tyre encounters more water than it can dissipate. It may take you a second to realise what’s happening, but the tell-tale signs include your steering feeling lighter and the rear of your car may start to veer. At this point, simply take your foot off the accelerator and depress the clutch. Keep a firm grip of the steering wheel, avoid any sudden steering movements, and stay calm. As your car slows down naturally and the tyres regain grip, continue driving at a reduced speed. If you can, try using the drier tracks left by the car in front of you as there’ll be significantly less water for your tyres to remove, but don’t forget to double your stopping distance in the rain.
Why tyre pressure matters
Tyre pressure and the overall health of your car tyres affects your driving, so maintaining correct tyre pressure is vital for your vehicle handling, overall performance, good fuel efficiency and load carrying capabilities. Many newer cars have a helpful tyre pressure monitoring system to alert you when your tyre pressure is too low, but you should still be aware of the warning signs and ready to top-up your air. Under-inflated tyres will take more engine power – and more fuel – to get the same amount of mileage. So, if you’re having to refuel more often, or sooner than you’d usually do, it’s time to check your tyre pressure. You won’t be able to see from a visual glance, but tyres under-inflated by 15 PSI can use 6% more fuel, that’s the difference between averaging 40mpg and 42mpg. If you feel that your vehicle is swaying into turns, taking too long to turn compared to normal, or just feels a bit off when it comes to steering and manoeuvring, low tyre pressure could be to blame. Again, if your car is taking longer than usual to come to a complete stop, it could be the pressure as tyres can’t grip the road as well when they’re under-inflated. In case you don’t already know, your vehicle handbook will tell you what your correct pressure should be. Alternatively, you may find a small sticker with the tyre pressure inside the fuel filler flap or on the drivers’ door edge. This will give you a figure in pounds per square inch (PSI) or BAR pressure which is a metric unit of atmospheric pressure equal to 14.50 pounds per square inch. It’s worth noting pressures are given for cold tyres that haven’t been driven for at least two hours, so make sure when you check yours that your car has been stationary for a while. Ideally you should do this every week, and definitely once a month.
It’s worth noting that you can get different air-pressure readings depending on which garage forecourt you use when checking your tyres. Trading Standards says drivers have the right to expect an accurate reading (where they pay for the service) and that gauges should be recalibrated at regular intervals, ideally every six months. However, this is often not the case.
Also, many handbooks list pressures for cold tyres, but when you drive to the garage, the tyres warm up and pressure increases. So even with an accurate gauge, you are likely to be underinflating your tyres. The solution is to buy a gauge and check the tyres yourself – a combined digital gauge and pump costs from around £20-£35, for example, at Halfords.
Tyre pressure checks
The Highway Code says check your tyre pressures weekly, but is this really necessary? The answer is yes because tyres can lose air suddenly through an impact such as hitting a pothole, speed hump or kerb – and air seeps through the rubber gradually anyway. On average, a tyre loses one or two pounds of air per month in cool weather, and more when it is warm. If you are 10 per cent low on air (say 3psi below the recommended 30psi), you can waste one third of your tyres’ tread life through drag. Not only that, but under-inflated tyres can cost you up to a mile per gallon in fuel economy because the rolling resistance is greater.
As for handling, correct inflation is very important. Low pressure reduces braking performance and can affect your ability to steer and grip the road. Your suspension has been designed to suit a particular tyre size inflated to a specific pressure and anything less reduces performance. You should pump up your tyres to the pressure stated in your car manual – not the maximum pressure embossed on the side of the tyre. Also, check your pressures when the tyres are cold, when you haven’t driven more than a mile or two. Otherwise, you’ll get an incorrect reading because air expands when it heats up.
Under-inflation is one of the most common causes of tyre failure. Excessive sidewall flexing causes the tyres to run hot, especially at motorway speeds during hot weather. The build-up of heat can lead to tread separation or a blowout. So for optimum safety, performance and economy, make that weekly check.
It’s an oft-repeated myth, but reducing your tyre pressures will not help your grip on snow. Your tyres are designed to function at a certain pressure and changing that could be dangerous. The most important thing is to make sure you have sufficient tread depth. This means at least 1.6mm and in snow you should aim for 3mm. To check, use a 20 pence piece. Simply place the coin in the main grooves that run round the tyre, if you can see the outer edge (border) of the coin it means your tread depth is less than 3mm and you should replace the tyre.
It may sound an unlikely tip, but keep a bag of cat litter in your boot, it can help grip the road and get you out of trouble if you get stuck.
Pump up to cut down
Under-inflated tyres create more resistance when your car is moving, which means your engine has to work harder, so more fuel is used and more CO2 emissions are produced. Simply checking and adjusting your tyre pressures regularly, and before long journeys, can help reduce fuel consumption and increase the life of your tyres. Take note, for every five per cent a car’s tyres are under-inflated, fuel consumption increases by one per cent.
Monthly car checks
At least once a month you should take the time for a more detailed check of your car. This includes checks on the following:
- Tyre pressures – using a reliable pressure gauge or garage air line
- Tyre condition – remember worn tyres can cost you points and put your car at risk
- Oil level – note how much you need to top up and get your engine checked if it seems excessive
- Wiper blades – worn wiper blades can be dangerous if they smear instead of wiping
- Screenwash – check this more often if you use it a lot
- Power steering fluid – your garage will have the right fluid if you need it
- Bodywork – get dents repairs quickly to avoid rust problems
- Exhaust – check your exhaust for rust and decay and replace it if required
Why not put a monthly reminder in your phone for the first of the month?