What is an 'Eco' tyre?

Combining eco-friendly low rolling resistance with tenacious road grip was a problem for tyre designers until they discovered the magic ingredient silicone

Designing a tyre to assist fuel economy by minimising friction while providing the road grip required for optimised braking and cornering would seem to be mutually exclusive objectives.

Yet that is the dilemma facing tyre companies as the focus of the auto industry in recent years shifts to assuage growing concern for the environment.

On the road, tyre distortion generates heat and adds to rolling resistance. Energy loss from this heat build-up is responsible for 90 per cent of a tyre’s rolling resistance, so anything that minimises this heat improves fuel efficiency and performance.

But although low rolling resistance tyres have been around for a long time it has been, until recently, accepted that such tyres might be good for saving fuel (and consequently reducing CO2 emissions) but they were not brilliantly effective in terms of road grip. Acceptable on a low-performance car but less so on a performance vehicle – which is undoubtedly the reason for low rolling resistance tyres, until recently, being relatively uncommon.

However in the 1990s the introduction of silica to replace the carbon black used in tyre compounds swung the balance and enabled tyre-makers to factor both low rolling resistance and road grip into a compatible mix. Hey presto, a seemingly impossible problem was solved.

Using silica as part of the tyre compound has brought higher degrees of flexibility and elasticity at lower temperatures, which result in improved grip and braking capabilities in cold weather. In a general sense, rolling resistance is typically reduced by about 20 per cent over a conventional tyre, with fuel economy benefits of as much as 12 per cent.

Other factors come into play of course when designing an eco tyre. For example Continental’s EcoContact 5 tyre has had a lot of design attention paid to the grip, flexing and load zones. The tread pattern is flatter than normal to reduce deformation in the contact area, and there are extra-thin sipes in the tread lugs that help remove and channel water to improve wet-weather performance.

The bottom line is noteworthy. According to claims made by eco tyre manufacturers, there are not only the emission reductions, but also a tangible effect on the wallet. For example Goodyear claims its Assurance Fuel Max tyre has the potential to save up to 320 litres of fuel during the life of the tyre (which is extended because of the design in the first place), equating to 320 litres, or as much as $480 at current petrol prices.

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