The stickers often carry the pressures for different wheel sizes and specifications. Each one is identified by a series of numbers and letters that describe the tyre’s size and width. You just need to find the sequence that matches the one on the wall of your tyres.
The pressure is usually shown in two formats: bar and psi. There are typically two sets of these. The lowest is for normal use, but you may well see another set of higher pressures for when the car is heavily loaded, increasing the weight that’s pushing down on the tyres.
Tyre pressures are typically between 30psi and 40psi (or 2 bar and 2.8 bar).
How to test your tyre pressure
Each of the inflators tested here has a gauge that gives you an instant readout that lets you know whether the tyre needs pumping. To use them, simply remove the dust cap from the valve on the tyre and push the end of the air hose over it, before pressing or releasing any catch to clamp it in place. Petrol station tyre inflators have pressure gauges, too, but these aren’t always accurate so it’s best to test using your own equipment.
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How often should you check your tyres?
The AA recommends checking your tyres every fortnight and doing so when they are cold, as the pressure increases slightly when your tyres warm up through driving. According to Michelin, one of the major tyre manufacturers, tyres that are under-inflated by 15psi (1 bar) will raise fuel consumption by 6% and increase your braking distance by 5m when travelling at 56mph.
It’s a good idea to examine each tyre’s condition at the same time, testing the amount of tread left and ensuring that there are no cracks or bulges that could lead to one of them bursting. It’s illegal to have less than 1.6mm of tread around the central part of the tyre, covering three-quarters of its area. One quick way to test your legality is to place a 20p piece between the grooves. If the border is still visible on the side touching the tyre, your tyres will probably need replacing soon.
What should I look for in a tyre inflator?
Size is probably the most important thing. The smallest inflators are around 20 x 20cm, so you can leave them in your car without losing too much luggage space. The best don’t skimp on the length of the power lead and air hose, which makes it easier to reach all four valves. Most can be preset to stop inflating when your tyre reaches the correct pressure.
Larger inflators include rechargeable batteries, which make them completely portable. These are a better option if you want to pump up, say, bicycle tyres, without having to wheel the bike next to your car. You may also need a larger inflator for tyres that need higher-than-average pressures, such as a larger van or campervan.
What about extras?
With mini torches, adaptors and USB ports, some tyre inflators sound like they’ve dropped out of a Christmas cracker, but these features can come in surprisingly handy. Any light source can be useful when you find yourself having to inflate a tyre late at night, while adaptors allow you to pump up bicycle tyres, children’s toys and footballs.
Some inflators have 12V ports so they can effectively be used as an extension lead that connects other accessories to your car’s power. If your car isn’t fitted with a USB port, it’s useful to have a tyre inflator with this feature so that you can charge a tablet or smartphone on the road.
How we test tyre inflators
We test tyre inflators by timing how long it takes to inflate a 15in tyre from 20psi to 30psi, taking note of the pressure displayed before and after inflation. We measure the noise levels during operation. We check the accuracy of the display, as well as verify the length of the hose and of the power cord. We evaluate how easy it is to connect the inflator to the tyre, and how easy it is to use. Finally, we take a look at any accessories, including bags or cases and adaptors for balls or inflatables.
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