Motorists could be throwing away more than one hundred pounds per year by making a very simple mistake.Not keeping on top of one particular area of car maintenance can have costly ramifications, it has been calculated.The job in hand takes just minutes to complete at home or at a fuel station, but can have a major impact on your bank account, according to controlled tests conducted this month.Driving a car with its tyres under-inflated by one bar (14.5psi) is estimated to cost an extra £150 a year in fuel, according to research by What Car?. That’s enough to pay for 37.5 takeaway coffees at £4 a cup.Experts who carried out the tests said that while there is a financial hit when it comes to not inflating tyres correctly, there are also safety implications of driving with too little air in your tyres that make the 'most compelling argument for checking tyre pressures regularly'.Driving a car with its under-inflated can cost motorists hundreds of pounds in wasted fuel, according to a new studyCar owners driving with tyres one bar (14.5psi) below the recommended pressure is estimated to cost an extra £150 a year in fuel, says What Car?What Car? conducted lab tests of three identical new tyres inflated to different levels to measure the rolling resistance or friction each tyre generated as it rolled along the road. One tyre was inflated to the recommended 36psi (2.5bar), the second to 22psi (1.5bar) and the third to 51psi (3.5bar).The under-inflated tyre suffered a 4.5 per cent increase in rolling resistance compared with the correctly inflated one, meaning the car would use an additional £1.50 worth of petrol for every 100 miles driven if four of them were fitted to an Audi A3 1.5 petrol.Work that up into an annual mileage of 10,000, and it represents an extra £150 on fuel.How incorrectly inflated tyres impact braking and handlingDuring further What Car? testing on wet and dry handling tracks, an Audi A3 1.5 petrol fitted with all four tyres under-inflated to 22psi took 1.3 metres longer to come to a halt from 50mph than the same car with four correctly inflated tyres (36psi). This additional stopping distance means a car is far more likely to crash into another vehicle in front or hit a pedestrian. The low-pressure tyres also lost grip on a wet road surface 5mph sooner than the correctly inflated tyres.Handling was also adversely affected when the tyres were deflated to 22psi. In this condition, the test car took a second second longer than the car with correctly inflated tyres completed a circuit of the wet handling track, and 1.8 seconds longer to go round the dry handling track.Although the under-inflated tyre had 4.5% less rolling resistance than the correctly inflated one, meaning it would use less fuel, there are compelling safety reasons why cars should not be driven with such low tyre pressureThe final test conducted highlighted the serious threat to safety posed by having a single under-inflated tyre, which replicates the car having a slow puncture. With the rear nearside tyre deflated to 22psi, the car skidded so violently on the wet track that it was flung off the Tarmac and onto the grass, stopping it from completing a test lap.What Car? consumer editor, Claire Evans, said: 'It’s good to know that you’ll save money on fuel if your car’s tyres aren’t over-inflated, but it’s the safety implications of driving with too little air in your tyres that make the most compelling argument for checking tyre pressures regularly.'Our main tyre test also highlights the significant difference in the handling and braking abilities of different tyres. 'Poorer performing tyres can take up to three metres longer to stop than the best tyres.'And this could be the difference between having a near miss or hitting another vehicle in an emergency situation.'Although the over-inflated tyre had 1.5 per cent improved rolling resistance than the correctly inflated one, meaning it would use less fuel, there are compelling safety reasons why cars should not be driven with such high tyre pressure too.
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