How did you choose your last set of tyres? The chances are that you simply asked for the cheapest option or told the garage to fit tyres of the same brand and type as those being replaced. The truth is that most of us lack the knowledge to make informed choices about the subject, a worrying state of affairs given that tyres are fundamental to the safety, comfort, performance, fuel economy and running costs of our cars.
But new EU regulations due to be implemented in November 2012 should substantially improve matters. These will require customers to be provided with information about each type of tyre in respect of three important areas of performance – fuel economy, wet-weather braking and external noise levels. Performance ratings for each of these will be shown in the form of bar diagrams similar to those already used to display the energy efficiency of washing machines.
Tyre buyers won't just be better informed, though – the tyres should be better too. There is, apparently, quite a bit of "stretch" built into the rating system so that tyre-makers will have an incentive to improve their products. What that means in practice is that the top "A" grade (the lowest grade will be a "G") will initially be hard to come by, and a lot of the tyres on sale today won't pass new threshold standards at all, and will therefore have to be withdrawn from sale. According to one of the world's leading tyre manufacturers, Michelin, 30 per cent of the tyres on sale today will not qualify for a rating under the standards set for 2012, while up to 70 per cent of today's tyres probably wouldn't meet tougher requirements planned for 2016.
Assessing tyre performance fairly and accurately is surprisingly difficult; so much depends on driver behaviour, the characteristics of the car to which the tyres are fitted, road surfaces, weather conditions and so on; apparently, the relative performance of different brands can even vary according to the size of tyre. Nevertheless, the big tyre manufacturers are putting a lot of effort into this area as the introduction of the new regulations approaches, and I recently had the chance to see how Michelin is tackling two of the three areas covered by the new ratings in tests carried out by the German testing and certification body TÜV SÜD at a test facility near Berlin run by the German motoring club Adac. Work on the two areas demonstrated by Michelin – fuel consumption and wet-weather braking – is especially important as the precise grading structure still needs to settled before the new system can be introduced.
While the energy expended in the manufacture, distribution, recycling or disposal of tyres is significant, the biggest factor in the environmental impact of a given tyre over its life is how it contributes to the fuel consumption of the vehicle to which it is fitted. That's a question of rolling resistance. Michelin demonstrated two separate tests: one isolating the impact of rolling resistance directly, and a second showing its impact on real-world fuel consumption. The first test involved three identical cars fitted with different brands of tyre, which were released from a ramp under the same conditions in order to see which would roll furthest. The differences between tyres was visible, with, in this case, a car fitted with Michelin tyres having an edge over the others which were fitted with Continental and Bridgestone alternatives.
A second test, using three Volkswagen Golfs driven over a mixed test route, showed the real-world impact of these differences in rolling resistance on fuel consumption. Drivers and tyres were switched regularly in order to cancel out the impact on fuel consumption of slight variations between different examples of the same model of car, or differences in driving styles, in order to isolate the variations accounted for by tyre type. In the test I witnessed, overall fuel consumption was 4.56 l/100km (litres per 100 kilometres) when the cars were fitted with a Michelin tyre, and 4.68 l/km and 4.76 l/km respectively for typical Continental and Bridgestone alternatives. These are very small differences but they mount up: over a year's motoring of 15,000km, the gap in overall fuel consumption between the best and the worst of these results would be 33 litres, which is worth about £40 at today's pump prices.
For the wet-weather braking test, I was able to take to the wheel myself. This involved braking a Mercedes E-Class as hard as possible from 80 to 20 km/h on wet asphalt. It takes a certain amount of practice to brake quickly enough and hard enough for the test, which is repeated over and over again, rotating tyres and drivers in order to eliminate any bias, under conditions that are strictly controlled by an ISO standard. In practice, braking takes place from a speed slightly in excess of 80km/h to rest, but sophisticated testing equipment measures just the 80 to 20km/h portion and rejects any attempts that fall outside the parameters set for the test to protect the integrity of the results. Michelin has conducted full tests for two sizes of summer tyre and one size of winter tyre, and sportingly published the results, even though its tyres only "won" the two summer-tyre categories and were slightly shaded by some competitor products in the winter-tyre category.
While the new regulations should greatly help to increase buyers' understanding of tyre performance, and provide the tyre manufacturers with an enormous spur to improvement, they are not entirely comprehensive; Michelin, for example, traditionally lays a great deal of emphasis on minimising wear, which won't initially be covered. In the long run, it would probably be desirable to extend the grading regime to cover as many characteristics as possible, as there are so many trade-offs involved in the design of tyres. Early eco tyres designed to improve fuel consumption, for example, were sometimes criticised for lacking grip. If the tests cover as many parameters as possible, buyers will be in a better position to see where these trade-offs lie and make informed decisions.
One area of potential difficulty concerns the method of displaying the mandated information about tyres in a way that makes it easily accessible to customers. It's easy to display the energy-efficiency ratings of a washing machine with a simple sticker, but tyres are handled extensively as they are delivered, loaded on to racks or rolled around a garage, reducing the chances of any sticker staying stuck for very long.
One side-effect of the new regulations may be to make life more difficult for future importers of cheaper tyres from countries such as China. As one Michelin executive put it: "It is a consequence, but it is not an aim of the programme. Are we crying about it? No." I suspect, though, that established tyre-makers hoping that the new rules might actually make life easier for them, rather than more difficult, could be disappointed. Tyres from Japan and Korea, like the cars made in those countries, used to be regarded sceptically, but soon started to make the grade. I'm not sure that Chinese cars or tyres will be any different.Reuse content