The EU is introducing new labelling legislation from November 2012, which is designed to help consumers, company drivers and fleet managers choose the right tyre to cut noise and emissions and improve fuel economy. Under the new legislation, all tyres produced after July 2012 (and on sale in the EU from November 2012) will need to be accompanied by a label at the point of sale providing information on three specific tyre performance categories: wet grip, fuel efficiency and exterior rolling noise.
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 decibels (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.
In addition to labelling laws, the EU will be raising the standards for tyre rolling resistance, noise and wet weather braking performance. New regulation will require reductions in rolling resistance in two stages to be introduced in November 2012 and November 2016, with the entire market required to comply with the new standards by 2018. Further reductions in noise will also be required, with implementation across the tyre market required by 2012.
Rolling resistance is the resistance that occurs when a tyre rolls on a flat surface. As the tyre rotates under the weight of a vehicle, it experiences cycles of deformation and recovery, loosing energy as heat. Low rolling resistance tyres are designed to minimise this heat loss, thus reducing the amount of energy needed to drive a vehicle forward.
Rolling resistance can be expressed with the rolling resistance coefficient (RRC), which is the value of the rolling resistance force divided by the wheel load. A lower coefficient means the tyres will use less energy to travel a certain distance.
Materials which flex more and bounce back more slowly exhibit greater rolling resistance than materials which flex less, such as steel, or materials which bounce back more quickly, such as silica. Low rolling resistance tyres often incorporate silica in their tyre tread compounds to reduce energy loss without compromising traction. Other factors which affect the amount of rolling resistance generated by a tyre include tyre inflation pressure, tread compound, tread design and temperature.
Tyre rolling resistance determines 20-30% of a vehicle's total fuel consumption, so lowering the rolling resistance of tyres can lead to significant fuel savings and reductions in CO2 emissions. There is currently a with a 10% fuel consumption difference between the best and worst performing tyres on the market.
Vehicle noise can generally be divided into two categories: power train sources (including engine, transmission, driveshaft etc), and rolling noise (created by tyre/road surface interaction). Tyre rolling noise is the dominant source of noise from cars at speeds above 25mph.
Tyre noise is measured in decibels (dB) -a logarithmic unit which indicates sound pressure level. Reductions in tyre noise are sometimes measured in dB(A), which indicates that the measurement has been ‘A-weighted’. This means that a filter has been applied to reflect the way in which the noise will be heard by the human ear.
Generally, tyre noise is measured according to the external noise that it creates. The range between the noisiest and the quietest car tyres is currently around 6-8 dB(A). For truck tyres, the range is about 10dB(A). A 3dB(A) results in a halving of noise in sound energy terms and a 10dbB(A) reduction halves perceived noise, so quieter tyres can achieve significant reductions in traffic noise.
Quieter tyres also reduce internal noise. Studies have shown that there is a strong link between internal and external rolling noise around the 1000 Hz frequency range, which are the most annoying frequencies for human ears.
Tyre noise is influenced by a number of factors, including tread pattern. In the past, wider tyres were much noisier than narrower tyres but tyre width no longer appears to be a significant parameter for noise any more - with the exception of extremely wide tyres, which still tend to be noisy.
The safety of tyres is generally measured by their wet grip performance, which reflects the capacity of a tyre to brake on a wet road. There are other parameters which are relevant to the safety of a tyre (road holding ability, directional control, deceleration ability on wet and dry surfaces at high speeds and aquaplaning behaviour) but existing testing methods make it possible only to measure wet grip.
When EU labelling law is introduced, wet grip will be rated on a sliding grade scale from A to G. the difference between each grade means an increase or decrease in stopping distance of between one to two car lengths (3-6 metres) when braking from 50mph. The difference between the best and worst performing tyres is more than 18 metres stopping distance.
Not necessarily. Advances in tyre technology mean that there are now many premium tyres on the market which achieve low rolling resistance and low noise as well as good wet braking and aquaplaning performance.
The introduction of silica to a tyre’s tread compound, for example, reduces tyre rolling resistance whilst at the same time improving a tyre’s handling and steering capability. Silica has been shown to offer a 15% increase in wet grip, as well as improving traction on icy roads.
Whilst premium tyres can achieve energy efficiency and low noise while remaining safe, tests have shown that some budget tyres compromise on safety. In tests carried out by What Car? Magazine, budget tyres took an average of 14 metres – the length of an articulated lorry - longer than premium tyres to pull up from 70mph. In the dry the worst budget tyre still took up to five metres longer to stop then the top premium brand.
Yes. Although the new EU regulation on tyres will not take force for a few years, there are already tyres on the market which exceed the new standards for rolling resistance, noise and wet grip. Tyre manufacturers are also ahead of the game when it comes to providing information about their tyres, and many are already in the process of preparing databases with information on the rolling resistance, noise and wet grip values of their tyres.
There is some evidence that fuel efficient tyres currently come at a small price premium. However, this will be paid back by the fuels savings achieved. The payback period for switching to the most fuel efficient tyres from average tyres is currently estimated at around 6-8 months for car tyres, 2.5 months for van tyres and 5 months for truck tyres. The price premium for fuel efficient tyres is likely to reduce as tyre technology develops and demand for low rolling resistance tyres increases. There is no evidence that low noise tyres come at a price premium.
Tyre manufacturers claim that the most energy efficient, low noise and safe car tyres can also achieve long wear life. There is some evidence that energy efficient truck tyres have slightly reduced durability, but in-use tests have concluded that the fuel cost savings achieved through switching to these tyres more than outweigh the tyre replacement costs.
Yes. Tyre manufacturers are now offering retread tyres which offer the same low rolling resistance technology and low noise tyres as new tyres.
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