The real danger of under-inflated car tyres – What Car?


Correct tyre pressures are displayed in the door jamb and the vehicle's manual
Fleet operators are being urged to check tyre pressures regularly after new research revealed the serious cost and safety risks of incorrect inflation. In lab tests, three identical new tyres were inflated to different levels to compare rolling resistance. One tyre was set at the recommended 36psi, one under-inflated to 22psi and one over-inflated to 51psi.

The under-inflated tyre showed a 4.5% increase in rolling resistance, meaning a vehicle like an Audi A3 1.5 petrol would use an extra £1.50 of fuel per 100 miles if all four tyres were similarly under-inflated. Over a year, this could add £150 to fuel costs for a car covering 10,000 miles.

Tyre pressure gauges are available from as little as £10


Safety concerns were even more striking. Under-inflated tyres increased braking distance by 1.3 metres from 50mph and lost grip on wet roads 5mph earlier. Handling was also compromised, with slower lap times and a serious loss of control during a test simulating a slow puncture, where the car skidded off the track.

The wider testing also revealed major differences in tyre performance between brands. The Continental PremiumContact 7 scored highest overall, while the Triangle EffexSport TH202 came last. Michelin’s Primacy 5 was praised for its fuel efficiency, but safety remains the top concern.

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