environment magazine

Campaign For Better Tyres

By Catrina Perkins, Campaign manager - Campaign for Better Tyres

As petrol prices rise and the cost of transport to the climate becomes more apparent, increasing attention is being paid to the potential of alternative fuel technology such as electric and hydrogen fuel cell vehicles. However, with costs of these technologies still high compared to standard combustion engines, it will be some time before there is sufficient uptake to make a real difference to transport emissions. Until prices come down, it is important to look at how we can make our current vehicles more efficient – both through improvements to combustion engines and through more efficient components. One often overlooked component, which can make a big difference to fuel efficiency and emissions, is tyres.

Many of us barely think about our tyre choice, often leaving it to our garage or tyre fitter to decide which model we choose. If we do search around, it is usually to find the cheapest deal. But as the only part of our vehicle that makes contact with the road, tyres play a vital role in determining how much fuel we use on a journey, how much carbon our vehicle emits, how much noise it makes and how quickly it can stop in an emergency.

Tyre technology is developing rapidly and tyres are generally more efficient, quieter and safer then ever. However, there is still a big gap between the best and worst performing tyres on the market, with the best able to reduce fuel consumption by 10%, cut rolling noise almost in half and reduce stopping distances in the wet by as much as 18 metres compared to the worst.

Premium vs Budget

So why do tyres perform so differently? Tyre design is a complicated matter, which usually involves a trade off between different performance factors. In order to improve the energy efficiency of a tyre, for example, it is necessary to reduce rolling resistance, which is the friction that it produces as it rolls along a road. In the past, this meant compromising grip because grip is best served by rubber compounds which absorb high levels of energy, while reducing rolling resistance requires compounds which absorb low levels of energy. Premium tyre manufacturers have managed to overcome this problem by replacing certain quantities of carbon black with silica in the tyre’s tread compound. Silica can reduce rolling resistance by as much as 20% whilst also improving grip by as much as 15%.

Further developments of tyre tread compounds and tyre tread patterns mean that manufacturers have also managed to reduce tyre rolling noise, which is the dominant source of vehicle noise at speeds above around 25mph.

However, all of this technology comes at a cost and while premium manufacturers are finding ways to balance tyre design, some budget tyres still compromise one performance factor for another, offering reduced rolling resistance or noise at the expense of safety performance. In recent tests carried out by What Car? Magazine, budget tyres took an average of 14 metres longer – the length of an articulated lorry – than premium tyres to stop from 70mph in wet conditions. In dry conditions, the budget tyres took up to five metres longer to stop than the top premium brand.

Choosing better tyres

New EU tyre legislation, due to be introduced next year, will make it easier for consumers and fleet managers to compare tyre performance and choose the best tyres to reduce fuel consumption, cut vehicle noise and improve road safety.

The European Commission has agreed two separate pieces of tyre legislation, both to be introduced in November 2012. The first - EU Regulation (661/2009) on type-approval requirements for the general safety of motor vehicles and tyres (http://www.etrma.org/public/Pdf%20from%20July/2008-316%20Final%20text.pdf)-  sets stricter type approval standards for tyres on noise, rolling resistance and wet grip.

The new regulation will require reductions in rolling resistance in two stages to be introduced in November 2012 and November 2016, with entire market implementation by 2018. Further reductions in noise will also be required, with implementation across the tyre market required by 2012.

The European Commission’s original proposal was to introduce the new standards by 2016, but the European Parliament caved to industry pressure and added a two to four year grace period before all tyres have to comply, with a further 30 months when retailers can sell off existing stock. This delay has been criticised by some environmental and noise groups, who argue that the time-delay will limit the effectiveness of the new regulation.

The second piece of legislation - EU Regulation (1222/2009) on the labelling of tyres with respect to fuel efficiency and other essential parameters (http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:342:0046:0058:EN:PDF)- will require all tyres produced after July 2012 and on sale in the EU from November 2012 to be accompanied by a label at point of sale providing information on three specific tyre performance aspects: wet grip, fuel efficiency and exterior rolling noise.

The labels will look similar to the energy labels already used for white goods and passenger cars.  Wet grip and fuel efficiency will be rated on a sliding scale from A to G, with A being the best performers and G being the worst. Noise levels will be split into three categories and measured in decibel (dB) in comparison with new European standards on noise levels to be introduced by 2016. The labels will bear either one, two or three black sound waves, with one indicating 3dB less than future European limits, two demonstrating compliance with future European limits and three demonstrating compliance only with current European limits.

Tyre maintenance

It is also possible to drive down a vehicle’s running costs and emissions through the proper maintenance of tyres. Running on under-inflated tyres, for example, can increase fuel consumption by as much as 4%. According to research from Michelin, over 370 million litres of fuel are being wasted each year as a result of under-inflated tyres, costing UK drivers more than £440 million pounds. It is estimated that this wasted fuel results in the dumping of over 2 million tonnes of carbon dioxide CO2  in the atmosphere each year.

Under-inflation also causes tyres to wear more quickly, reducing their lifespan by as much as 45% and resulting in 200 million prematurely wasted tyres in the world each year.

Another aspect to consider is wheel alignment, which can be affected by hitting a kerb or pothole, or if there is wear to the steering or suspension components of the vehicle. Incorrect wheel alignment increases drag on the tyres (rolling resistance), which increases fuel consumption and emissions. According to www.trackace.co.uk, an average car wastes 10% of fuel at 2° misalignment. Wheel alignment also causes tyres to wear unevenly, which can result in them needing to be replaced more often.

Future role

By combining careful maintenance with today’s tyre technology, we could make a significant difference to the fuel consumption of the UK and European fleet. If we were all to choose the best performing tyres on the market right now, we could save 6.6 million tonnes of oil a year in Europe by 2020, which is as much as the annual consumption of Hungary. We could also cut CO2 emissions by as much as four million tonnes per year - equivalent to taking 1.3 million cars from the roads – and cut traffic noise by a third.

Hopefully the new EU tyre labels will be a step forward for raising awareness about tyre technology and help ensure that these vital components finally get the attention and recognition they deserve.