New US Tyre Testing Standards
In the aftermath of the Firestone tyre recall in the USA, Congress ordered the National Highway Traffic Safety Administration to look at the way tyres are tested and to come up with a testing program to improve safety. This the NHTSA has done and details of the new tests for passenger and light truck tyres – the first change in tyre safety standards since 1967, incidentally – have been revealed. The tests will apply to all tyres from 1st June 2007 and, according to NHTSA Administrator Dr.
Jeffrey Runge, “These new performance requirements will improve tyre safety” with the agency estimating that at least four lives a year will be saved and 102 injuries prevented.Most tyres on the market will already comply with the proposed standards and the NHTSA reckons that between five and eleven per cent of tyres will have to be re-designed or modified. The total cost to the manufacturers will be $31.
6 million, but this is in contrast to the original NHTSA proposals, which would have cost manufacturers almost ten times as much, and which anything up to 30 per cent of tyres would not have passed. Among the tests not included is one for measuring the strength of a tyre’s performance on hazardous surfaces and a test that measured the effects of ageing.The new testsSo what are the new criteria that the tyres have to meet? The speed test involves running the tyres at speeds of 87, 93 and 99 miles per hour for 30 minutes at a time (current test speeds are 75, 80 and 85 mph).
A tyre will be deemed to have passed if there is no visual sign of tread separating or cracking and if the tyre pressure is not lower than the initial pressure.The endurance test will last for 34 hours at variable speeds and loads. Tyres will run at 75 mph for four hours, carrying 85 per cent of the tyre’s rated load.
This is followed by six hours running with 90 per cent of the load and 24 hours with 100 per cent of the load. This test is 50 per cent faster and 50 per cent longer than current requirements.A new test is included to measure performance even if the tyre is under-inflated, designed to simulate long-distance family travel.
This means running the tyre for 90 minutes at 75 mph, at the level of under-inflation that triggers the vehicle’s tyre pressure monitoring system. Another NHTSA introduction is that all new cars and light trucks will have to be fitted with a TPMS.The reaction of the tyre manufacturers is mixed, as the new standards will involve them in extra costs, yet they cannot be seen to be objecting strongly to something which is designed to save lives.
Nevertheless, the Rubber Manufacturers Association did lobby for light trucks to be tested at lower speeds, but the NHTSA ignored this request. At the end of the day, the manufacturers will have to bite the bullet and conduct the tests in-house, but they have the consolation that things could have been much tougher – and much more expensive..