In the quest to reduce car emissions, tyre makers are trying to play their part. Shane O'Donoghuetries out Michelin's energy-saving tyres
NOT SINCE the 1973 oil crisis has there been so much focus on the fuel consumption of our beloved car. The emissions of CO2are more or less directly related to the amount of a fossil fuel burned in an engine, and it is the figure by which all cars are now judged.
Given the draconian legislation likely to be enforced on the world's car makers in the next decade, it's unsurprising that every component on the car is under scrutiny.
Remarkably, little is ever said about the single part of the vehicle that is in contact with the road surface. Obviously the friction necessary between tyre and road consumes energy, but it was eye-opening to be told that it can be up to 20 per cent of the total energy used in propelling the car, ie a fifth of the fuel you put into the tank is expended in this manner.
This figure can be significantly decreased by reducing the "rolling resistance" of the tyre. However, that's not the full story.
Traditionally, a reduction in a tyre's rolling resistance compromises its safety in terms of braking distances and cornering grip. Michelin claims to have cracked the problem though, with the introduction of its new Energy Saver tyre. Apparently, it reduces rolling resistance by about 20 per cent, while maintaining competitive durability and safety.
Motors spent a day driving various models at Michelin's test facility in France, with the new Energy Saver tyre pitted against competitors' offerings. The quantitative experiments included an "independently" monitored fuel economy run, where two supposedly identical Mercedes C-Class saloons were driven at 90km/h for 102km, one on the new Michelin tyre and the other on a "leading competitor".
The certified results were 6.75l/100km for the Michelin-shod car, with 7.14l/100km achieved on the other. It's a modest gain, but significant over the life of the set of tyres.
Our next experiment involved an emergency stop on a soaking wet surface in the new Fiat 500. On-board GPS systems measured the stopping distance from a speed of 70km/h.
Each driver posted a time in a Michelin-shod car and another fitted with competitor tyres. Averaging the results from nearly 150 tests, it's no surprise that the Michelin tyre came out on top, stopping nearly three metres shorter on average.
Leaving cynicism aside, these tests at least show that there is no obvious disadvantage to the Energy Saver tyre. An entertaining handful of laps at the wheel of a VW Golf on the wet handling circuit confirmed the same.
Depending on driving style and mileage, the quoted figures will lead to modest savings over a year, though Michelin claims that over the life of the Energy Saver tyres, one of them is completely paid for by the gains. More significantly, it's possible that a car maker could reduce its model's emissions rating by using "greener" tyres as standard.
Peugeot, for instance, was the first car maker to fit the new Michelin tyre on certain versions of its new 308, in the process managing to reduce its official CO2 emissions rating by four grams per kilometre.
Michelin isn't the only tyre maker marketing low rolling resistance tyres. Goodyear produces the DuraGrip, which is designed to offer less friction, yet employs the company's patented tread block design to significantly improve wet weather handling and braking.
Goodyear's claims are even bolder with regards to savings, stating that the fitment of a DuraGrip tyre can pay for itself within a year.
Naturally, tyres fitted as replacements by consumers will have no effect on a car's official emissions rating, so the tyre makers need to educate buyers as to the benefits.
Right now, the EU is readying a labelling system similar to that employed on white goods, with clear colour coding and lettering denoting the greenest choice.
Michelin is supporting this scheme, though both it and Goodyear Dunlop are also lobbying to include data such as stopping distances in the wet, as the proposed system only measures the rolling resistance.
Although tyre purchase is very much driven by price - it being a distress purchase - if the message is clear enough, then the buyer may consider other factors too in the future.