Semperit, one of Ireland's major tyre suppliers, is to exert pressure on the Government to demand a change in the EU-wide law relating to the minimum tyre tread level. Currently the minimum legal tread depth is 1.6mm, however, following research into vehicle stopping distances in the wet by MIRA (the Motor Industry Research Association), Semperit is looking for a doubling of the minimum depth to 3mm.
The independent research, which was funded by Semperit and the British Rubber Manufacturers Association, found that a car travelling at just 80km/h with tyres at the minimum legal tread depth, travelled for an extra 13 metres under heavy braking in the wet, when compared to a car with new tyres. MIRA says its findings provide compelling evidence that motorists should change their tyres at 3mm and not wait until they reach the minimum depth.
The tests also revealed that a car with tyres with a tread depth of 3mm, as recommended by various tyre manufacturers, car makers and safety organisations, had a 25 per cent better performance than those with the minimum legal tread. This means that the car travelled eight metres - or the length of two family cars - less.
"If motorists replaced their tyres sooner, stopping distances would improve, accidents reduce and lives would be saved," says Adrian Walsh, chairman of Britain's road safety organisation, Roadsafe.
"You can be driving within the law, but still be very dangerous," adds Simon Aldworth, MIRA's senior engineer.
Although the research findings are not new - Semperit announced them some months ago - the decision by the company to pressurise the Irish Government has only recently been taken.
"These tests clearly show that even at moderate speeds, cars on tyres with the legal tread depth have a significantly reduced stopping ability. I don't doubt that worn tyres, even at or above the legally acceptable tread depth limit, are a contributory factor in many road accidents. For this reason, I believe that our road safety legislators need to look seriously at this issue, and Semperit Ireland will be presenting our concerns to the Minister for Transport," says Paddy Murphy, general manager of Semperit Ireland. "There is no question but that the legal tread depth limit should be raised to a safer level and the tyre industry needs to be more proactive in putting that message across to Government."
Although welcoming its competitor's decision, Bridgestone said that what was needed was not simply a change in the law, but rather an increase in enforcement. Bridgestone's Colm Cunnyngham says: "I would not be against the law being changed to 3mm. However, I would sooner be calling for stricter enforcement of the present rules."
The 1.6mm minimum tread depth was set in 1992 across the EU, and replaced the 1mm minimum that was set over three decades ago. The industry has long called for an increase of the minimum tread depth, originally to 2mm, but now, following this research, to 3mm.
The car manufacturers' industry standard in France is that tyres should be changed when their tread reaches 3mm, because of the severity of performance degradation that occurs below that level.
Aquaplaning occurs when the pressure of water in front of the tyre forces the water between the tyre and the road surface, which causes the car to skid. When hitting a sheet of water on the road surface, the advice is remain at a constant speed, or to very gently decelerate by taking your foot off the accelerator pedal, and avoid braking or any sudden steering movement.
Surprisingly, low profile and wider tyres are not as safe as tyres with a smaller contact area in the wet. As the weight of the wheel is spread over a greater area, the ground contact pressure is lower and therefore is less able to cut through the water. Think of it as trying to cut through butter with the flat of a knife rather than its cutting edge.
The more heavily loaded a car, the less distance it will take to stop in the wet. This illustrates the importance of pressure in the contact patch. It should be remembered that a light, high performance car with low profile, wide tyres may look great, but it will perform the worst in wet weather braking.
Although the Government is being pressured to call for a change in EU law to force other countries to adopt a 3mm minimum, in Britain the road safety organisation Roadsafe is taking a different tack - warning fleet managers that they have a duty under health and safety legislation to ensure the safety of their employees.
This, they say, can be improved by changing tyres at 3mm. Fleet managers in Ireland should take note. All new tyres must meet European standards for load/speed performance, this is shown by an 'E' or 'e' mark on their sidewall. It is illegal to sell or use tyres without this mark.
Most tyres have tread wear indicators, which are usually six or more small ribs across the bottom of the main tread grooves. When the tread surface is level with these ribs, the tyre has reached the minimum legal depth and must, by law, be replaced. It is advisable to check tyre pressure at least every fortnight, and only when the tyres are cold.
It is an indication of the reliability of new cars that motorists rarely, if ever, check their owner's manual. Manufacturers are now reporting that, when they inspect three-year-old trade-ins, it is the rule that few, if any, of the manuals had ever been opened.
Although it may be reassuring to note that new cars are so reliable, there is now a tendency towards accepting that a new car needs no maintenance accept for an annual service. This often leads to tyres being ignored, and this is costing lives.
To prove to sceptics that the call to increase the minimum tread depth is not yet another ploy by the tyre manufacturers to get motorists to buy more tyres more often, journalists and road safety experts gathered at the MIRA research centre in England to test the findings for themselves.
After performing emergency braking manoeuvres on a wet weather test track in a standard car fitted with tyres with varying degrees of tread depth that were all well above the legal limit, we were given the keys to a car with its tyres rubbed down to the legal minimum of 1.6mm.
The car we drove, a Rover 75, was legal in every way and could be driven straight from the test centre on to the main road. The instructions were clear: drive onto the wet surface at a certain speed and brake as if a child had just run out in front of you or a truck had just jack-knifed on the dual carriageway in front. Even before the brakes were applied it was clear that we no longer had full control of the vehicle. As soon as the car hit the surface water on the wet weather section, it began to aquaplane. Unnerving as this was, we accelerated up to the standard 85km/h, as would most motorists on a national road.
When the brakes were slammed on, the ABS began instantly to prevent the wheels locking as they began to aquaplane and skim across the surface. Because of the lack of adequate tread, the tyres could not perform their vital function of transferring the surface water away and so the car wanted to skid: the only thing preventing this was ABS.
Despite the best efforts of the electronic brake system, the car ploughed on and on. The distance travelled, which was measured by a professional satellite navigation system, was almost double that of a car with new tyres. Our car came to a halt some 12 metres further on than a car fitted with tyres that had the manufacturer's recommended 3mm minimum tread depth.
Twelve metres doesn't sound much, but it is the difference between stopping short of a truck that has jack-knifed in front on a wet, dark night and hitting it at a significant speed. Twelve metres when braking hard is the difference between life and death.
This was a shocking lesson about a piece of automotive equipment that is all too often ignored.