Unlocking the

secrets of worn


Michelin worn tyre testing
Michelin worn tyre testing, front
Michelin worn tyre testing, wet
Michelin worn tyre testing, side
Michelin worn tyre testing, track

MICHELIN believes the testing of worn tyres is closer than ever, meaning savings for the consumer and the environment.

For at least the last six years, the tyre manufacturer has called for the testing of worn tyres, arguing there is no link between tread depths at 1.6mm and increasing accident rates.

It has consistently highlighted that changing tyres at 3mm would cost individuals and businesses money and increase carbon emissions.

Currently, European regulation applied to tyres means that wet braking performance is only measured once, on new tyres. However, throughout a tyre's service life, this performance level - critical for safety - decreases.

So, there is nothing that prevents selling tyres whose braking distances might deteriorate dramatically during their period of use.

However, in March 2019, the European Union introduced the principle of a test on used tyres into the General Vehicle Safety Regulation, which is due to be adopted in autumn 2019.

A working group, led by France, has also been set up at the United Nations Economic Commission for Europe to define the procedures for these tests, the reference tyres and the regulatory thresholds that must be met.

Michelin says that if the testing or worn tyres is accepted by the regulators, it could save up to 128 million tyres per year in Europe with a CO2 saving of up to 6.6 million tonnes.

It would also save drivers up to 6.9 billion euros - around £6.2 billion - per year.

The company's argument is clear. Research has shown neither the different rankings established for new tyres nor the tread depth of the tyres can give an idea of their performance over time.

To know the real performance of used tyres, you have to test them.

To prove its point, it went to the OAMTC (Austrian Automotive, Motorcycle and Touring Club) Testing Centre at Teesdorf, near Vienna. There it showed how identical cars performed on a wet track with different tyres worn to the same tread depth.

The results were startlingly different with some worn tyres performing better under braking on a wet track than new tyres - something Michelin has long argued. The performance of different makes of tyres also differed greatly.

For new tyres, the wet braking test measures the distance required to decelerate a vehicle from 80 to 20kmh (50mph to 12mph) on a standard road surface with a water depth of 1mm - and to have 1mm of water on a road is an ‘exceptionally rare' event.

Michelin believes this is also the best way to test worn tyres as it meets the real conditions of the risks that a motorist may encounter on the road.

Though 1mm might seem low, research in Germany has shown that 99 per cent of accidents occur on dry roads, or wet roads with less than 1mm of water.

Research has also shown, in the event of heavy rain and reduced visibility, drivers reduce their speed by up to 40kmh (25mph).

Other research in Germany has shown that in 90 per cent of accidents on wet roads, motorists were driving at less than 50mph. And, most accidents - about 65 per cent - happened in urban areas.

Pierre Robert, Michelin's director of research and development, said: "Today, there are road tests only on new tyres. These only exist on the shelf. Tyre performance changes as soon as a consumer start driving them. As soon as a tyre is mounted on a car and drives, it starts to wear out, and the more worn it is, the more its performance changes.

"Some performance improves with wear, such as dry braking and fuel consumption. But, wet braking is the main safety performance that degrades, sometimes very severely, as a tyre wears, so it is a safety performance that should be systematically tested."

It is this that the regulatory authorities now seem to be moving towards.

Michelin says its objective is to ensure that each customer has relevant information on the performance of their tyres throughout their life cycle.

Mr Robert said there was now consensus in the industry on this and Michelin was not ‘a single player'. However, it was down to manufacturers' ‘choice' on the way forward.

Michelin has pointed out it spends more than 600 million euros a year (around £538 million) on research and development.

"How do you know you're safe on your tyres. Today, customers cannot know if they are safe on their tyres. Our objective is very simple - provide pertinent, transparent information. Clarity is the key," said Mr Robert.

Mr Robert said the potential change would be crucial as the world moved towards more autonomous and self-driving vehicles.

"The more the vehicle is equipped with safety features, the more the role of tyres is key," he said. "The safety technology eliminates the role of the drivers. What takes effect is the tyre. It is the sole connection with the road. It will be all the more important as cars are equipped with advanced safety features and become autonomous."

Mr Robert said Michelin was convinced the testing of worn tyres would be good for the industry as it would add more value to consumers.

Michelin, of course, introduced radial tyres which doubled the mileage performance life, he said. "Clearly, the strategy was not to sell more tyres," said Mr Robert.


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