A survey by the AA has found that 48% of cars could have underinflated tyres, meaning nearly half of drivers could be wasting fuel and compromising safety.
The results follow an earlier test by the AA where the Association found that driving with tyres 7 psi underinflated increased fuel consumption by nearly 8%.
AA PetrolWatch spokesperson Mark Stockdale says that after the test proved that underinflated tyres use more fuel, the AA wanted to know how many people might be driving on them.
“We thought there would be quite a few people with underinflated tyres, but we were surprised to find that it could be as high as half our private vehicle fleet,” he says.
“Underinflated tyres use more fuel and wear out faster, so they unnecessarily cost you money on both fronts, and they’re less safe.
“It’s like riding a bicycle with flat tyres. The effort you need to get a bicycle with flat tyres moving is far greater than if the tyres are properly pumped up.”
The AA survey involved a random sample of 150 vehicles undergoing a warrant of fitness at an Auckland AA Inspection Centre.
Only 17% of those tested had tyre pressures at or within 0.5 psi of the manufacturer’s recommendation.
Overinflated tyres wear unevenly, have less grip on the road and can affect braking ability. Underinflated tyres wear more quickly and affect cornering, braking and water dispersion, as well as increasing rolling resistance.
A vehicle with tyres 4 psi underinflated could be using about 4% more fuel. At current petrol prices this equates to about 7 cents more per litre and over a year would add about $100 to the annual fuel bill for the average motorist in a medium-sized petrol car, says Stockdale.
Read more tips for economical driving.