New research by What Car? highlights the risks associated with driving on incorrectly inflated tyres.
The study measured the rolling resistance of three new tyres when inflated to different pressures. One tyre was inflated to the recommended 36 psi (2.5 bar), with the other two set at 22 psi (1.5 bar) and 51 psi (3.5 bar), representing under-inflated, over-inflated, and correctly inflated tyres.
The under-inflated tyre generated 1.5% more rolling resistance than the correctly inflated one. In real terms, this could cost up to £1.50 in extra fuel for every 100 miles, based on an Audi A3 1.5 petrol. Over an annual mileage of 10,000 miles, that’s an extra £150 in fuel costs.
The research also highlighted the safety risks associated with under-inflated tyres. Tests on wet and dry handling tracks revealed that vehicles fitted with under-inflated tyres, travelling at 50mph, took 1.3 metres longer to stop than vehicles fitted with correctly inflated tyres. In wet conditions, poorly inflated tyres lost traction 5mph sooner than correctly inflated ones and showed noticeably worse handling. These tyres also took longer to complete a lap, adding 1 second on the wet track and 1.8 seconds on the dry track.
Claire Evans, What Car? Consumer editor 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.”
She continued: “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 that could be the difference between having a near miss or hitting another vehicle in an emergency situation.”
