Tyre safety alert

Text: Julie Sinclair / Photos: Nathan Morgan/Derek Goard

15th January 2008

More than one-third of motorists are dangerously negligent when it comes to maintaining their tyres, an Auto Express investigation has revealed.

During random spot checks, 36 per cent of the drivers we stopped were running on rubber that was over or under-inflated by at least 10 per cent on all four wheels – some by twice as much as the recommended rate. A further 27 per cent featured at least one tyre that was bald or had just-legal tread depth. Many motorists admitted they left their tyres unchecked for up to a year – so they were blissfully unaware of dangerous faults which could prove fatal in an accident.

But are drivers entirely to blame? In our undercover inspection of UK petrol forecourts, we found 39 per cent of sites had tyre pumps which were damaged, out of order or giving incorrect readings. So how did we discover all this? With the help of the RAC, we spent the day offering free tread depth and tyre pressure checks to motorists using a service station in north London – and the results were dismal.

Only one driver passed without fault. More than a third had at least one tyre that was inaccurate by more than 50 per cent, while one was 76 per cent out! BMW 3-Series owner Eleni Christou from Crouch End had a tyre inflated to only 7psi, instead of 29psi.

Still not shocked? Well, tyre pressures affect how quickly a car will stop in an accident. That’s because over-inflated rubber has a smaller contact patch on the road, which results in a significant reduction in grip. If they are under-inflated, a loss of rigidity affects steering control and cornering performance.

What’s more, neglecting your tyres will hit your wallet. A car driving at 56mph on rubber that’s under-inflated by 14psi uses an extra three per cent of fuel, says Michelin. And durability is restricted as well as economy. A spokesman for Kwik-Fit explained, “A correctly inflated tyre will last up to 5,200 miles more than one that is under-inflated by 10 per cent.”

We checked tread depths in our investigation, too. And although the drivers we stopped fared much better here, we were still shocked that 27 per cent were using at least one tyre that was bald or had just-legal tread depth. One 1997 Vauxhall Astra had four bald tyres! Owner Don Leavy of Cricklewood admitted, “I’ve had these tyres since the car was new.” That’s 10 years!

RAC patrolman Prakesh Patel explained, “There is no tread on these. And the rubber is feathering. I wouldn’t want to drive this vehicle on the motorway for any length of time.” To make matters worse, all four tyres were under-inflated by at least 10 per cent.

The minimum legal tread depth is currently 1.6mm – and one in five of our drivers had at least one tyre on or below that limit. This can have a dramatic impact on your vehicle’s halting ability. In an Auto Express investigation last year, we found stopping distances in the wet increase by up to 44 metres – around the length of 10 vehicles – when braking on 1.6mm of tread depth, compared to 3mm.

That’s one of reason why campaigners are calling for the legal limit to be increased. Faced with those stark facts, why were so many motorists leaving their rubber unchecked? Excuses were thin on the ground...

“It’s my husband’s job,” was the response from Honda CR-V driver Sarabajaya Kumar of Wood Green. Daihatsu Move owner Helen Sturz of Golders Green claimed, “I leave it until the MoT is due.”

However, the most common complaint was aimed at filling stations – and the frequent absence or inaccuracy of the tyre pump kit on forecourts. Veronica Piller of Hendon was driving a VW Polo with three over-inflated tyres – one was measuring 8psi more than the recommended pressure limit. Another had just-legal tread depth of 1.6mm. She told us, “I had them all checked about a month ago, and the garage said I didn’t need new tyres. It’s obvious now that he was putting far too much air in as well!”

VW Golf owner Josie Biciajowska, also of Golders Green, had four incorrectly inflated tyres – one by 33 per cent. She explained, “I filled these up two weeks ago. Often, the machine doesn’t work properly. They should make sure it does. I thought the car didn’t feel right or drive well. It’s so dangerous.”

We decided to investigate these drivers’ claims. Tyre pumps should be checked every six months for accuracy, according to Caltec ATC, a professional kit calibration firm from Knutsford, Cheshire. “Service providers have a duty of care to ensure pumps are in proper working order,” a spokeswoman told us. The manufacturers even recommend checks are done every three months. However, there is no legal obligation for filling station owners to do this.

A spokesman for the Tyre Industry Council (TIC) claimed, “I doubt this happens. A lot of pumps don’t work or are not accurate. But the operators may still charge anything up to 50 pence for air, blaming the cost on the expense of calibrating the kit.”

With the help of Caltec, we checked some sites for ourselves. We visited more than 80 filling stations across the country, where our expert used the pumps to inflate one of his own tyres to a set figure. He then checked the pressure with Caltec’s specialist kit – which has been calibrated on test equipment that’s accurate to standards approved by the United Kingdom Accreditation Service. We compared the two figures, with each pump being checked at 20psi, 30psi and 40psi.

Again, the results were surprising. A worrying 40 per cent of the sites had pumps which were not filling to the correct pressure. This ranged from inaccuracies of 1psi or 2psi to 14psi at one Tesco forecourt in Hertfordshire. Here, the pump was over-inflating, so a driver who thought he was inflating his tyres to 40psi was actually filling them to 54psi!

A certain margin of error is acceptable, according to Caltec. It says the industry tolerance level for tyre pumps is 2psi under or over the reading stated on the machine. Even sot, seven per cent of the sites we visited were still on the limit or outside of the range.

In our tests, the old analogue or linear pressure gauges were most likely to read incorrectly – 18 per cent gave inaccurate figures, compared to only three per cent of the digital units. Caltec technician Paul Banks explained, “The problem is that a handheld tyre inflator sometimes gets thrown to the ground after use. As this is where all the technology is stored, it’s much easier for it to break.”

That was true of the forecourts we visited. At one Jet service station in Enfield, north London, the lever was broken on the pump, making it virtually impossible to check our pressures. At another site in Islington, a missing nozzle meant the gun wouldn’t operate the tyre valve at all.

Yet inaccurate readings were not the only criticisms. We were amazed how difficult it was to find a forecourt with a pump that even worked! In fact, 19 per cent of the sites had machinery that was out of order – and frustratingly, half of these didn’t carry any warning signs. Our chart shows how many pumps were not functioning, damaged or gave wrong readings in each area.

A number of innovations are set to make it easier for motorists to check their pressures. A TIC spokesman told us, “It will soon be possible to get the correct figure for your car texted to your mobile.” A similar system will see tyre pumps automatically calculating the pressure when you punch in your registration number.

For now, though, it’s clear that drivers need to be more aware of the pressure in their tyres. If in doubt, take your car to a garage or a fast-fit tyre centre. Some operators will carry out a free pressure and tread check.

How to know what your tyre pressures should be
If you don’t know the correct pressures, check the owner’s manual. This should list separate figures (in psi or bar) for rear and front – the weight of the engine and gearbox means the fronts often need more air than the backs. The manual should also provide pressure figures for carrying a heavy load. These will be higher than standard.

Should you be unable to find your manual, most models carry the pressure ratings on a separate label, often stuck inside the driver's door. The figures may also be listed behind the fuel filler cover. If in doubt, log on to www.kwik-fit.com – this has a section which lists the correct pressures for your car when you type in your reg number.