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Award-winning tyres are put through their paces

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The choice of tyres you use on your car can have a profound impact on the cost of driving, both financially and environmentally.

Experts estimate that around 20% of the fuel used in every vehicle is accounted for by tyre choice, and in this eco-conscious age the major tyre manufacturers are doing their bit to minimise the impact their products have.

Most of the more recognisable tyremakers now have a low-rolling resistance tyre in their range. Rolling resistance is key to the efficiency of a tyre, and while all of the firms will tout the benefits of their own tyres, Michelin may have slightly more kudos behind them.

Michelin first introduced low-rolling resistance tyres in 1992, and has just seen its fourth generation tyre, the Energy Saver, awarded Tire (sic) Technology of the Year by Tire (sic) Technology International magazine in the US.

In an effort to spread the word of the benefits of low-rolling resistance tyres, Michelin invited Fleet News to a comparison demonstration of the Energy Saver tyre against its main competitors.

Michelin claims that using them could reduce tyre con-sumption rates by a quarter, and that vehicles running the tyres emit 4g/km of CO2 less than a competitor tyre.

Fleet management firm Arval, a keen advocate of the tyre, says a fleet of 200 vehicles could save £84,000 over three years.

Pierre Menendes, corporate and technical communications manager for Michelin, said: “One tank of fuel in five is used to make the tyres roll.

“Tyres all look black and round but they are not the same. Tyres generate heat, due to the bends and stresses they suffer on the road.

"All the time your tyre turns it deforms, it doesn’t stay round – the contact patch with the road is flat.”

Heat generated equals energy lost, and reducing heat loss boosts energy efficiency, meaning less fuel is needed to move the tyres.

“But the problem is that for grip you have to quickly heat up the surface of the tyre,” Mr Menendes says.

“A cold tread will not have the same level of grip. It’s a contradiction. If you want to improve rolling resistance you want to decrease heat build-up, but you have also decreased the heat build-up for the surface of the tyre.

"With standard tyre technology if your rolling resistance gets worse you get the better grip and vice versa.”

Michelin’s engineers say the answer lies with silica, the main ingredient in the compound making up Energy Saver tyres. Its properties make it possible for heat in the mass of the tyre to remain low while the surface temperature heats up fast.

“The traditional trade-off was also between traction and wear,” Mr Menendes continues.

“The Energy Saver has the same adherence but with the same level of wear. It is 10% lighter than our previous tyre, the Energy 3.”

Michelin says no other brand of tyre attains the same levels of grip, fuel savings and long-evity, and claims a 40% wear advantage.

It was ready to back it up with some demonstrations, independently monitored by French huissiers de justice, or professional witnesses.

 

Claims put to the test

TEST ONE – WET BRAKING

Longevity and environmental friendliness are all well and good, but tyres need to be effective on the road.

The first demonstration saw tests on a fleet of Fiat 500s equipped with 14-inch tyres.

As well as the Michelin Energy Savers, the cars sported competitor tyres in the form of Bridgestone B250s, Continental EcoContact3s and Goodyear DuraGrips.

They were tested on wet Tarmac, with both journalists and instructors invited to brake hard at around 50mph.

A GPS system measured the braking time from 43.5mph (70kph) to zero, to avoid inaccuracies in approach speed.

After dozens of runs, the results were averaged out and distance figures reached for the Michelin tyres and the combined competitors.

The results saw cars equipped with the Energy Savers stop in an average of 24.6 metres and the competitors in 27.4 metres – a 2.80 metre advantage.

This was borne out by my own experience – the Michelins seemed to dig in to the road surface towards the end of the braking time, and slip on the surface less than the other makes.

TEST TWO – WET HANDLING

This test was much less scientific – two identical Volkswagen Golfs and two Kia Cee’ds were equipped with a set of Energy Savers and a set of competitor tyres, and sent out on a wet handling track.

It was an opportunity to test the tyres back to back and, to be honest, there was very little difference.

Only when really pushing the cars – far more than one would do on the road – could any separation be detected, and although it was in the Michelin’s favour (again under braking) it was a miniscule difference.

Safe to say though, that the Energy Savers are certainly no worse than other low-rolling resistance tyres when it comes to performance on road.

TEST THREE – FUEL CONSUMPTION

This long-distance test saw two identical Mercedes-Benz C-Classes sent out to cover 102km around a test track.

Each car contained a driver and an independent adjudicator and had the air conditioning turned off before embarking on the journey at identical speeds.

One car was shod with Michelins, the other with Bridgestone B250s.

At the end of the test, the car running Energy Savers achieved fuel consumption of 41.8mpg, while the Bridgestone car made 39.5mpg.

CONCLUSIONS

With any demonstration organised by a party with obvious interests in the result it’s difficult to take the conclusions at face value, but Michelin seemed to take steps to ensure its tests were fair and the results independently verified.

Without back-to-back or long-term comparisons on the road it’s impossible to give a definitive opinion on the Energy Saver tyres compared to its rivals, but from the selective demonstrations it’s clear they are impressive in their own right. If the claims of potential savings from Michelin are even partially accurate, the latest low rolling resistance technology is worth looking into.
 

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