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Ysgol Ddreifio
Driving School
DRE
Delivering Real Experience
Based in Blaenau Ffestiniog, Gwynedd
Know About Tyres
Your tyres are a very important component on your car as these ensure that you stick to the road and remain safe under a wide variety of difficult, complicated and ever changing circumstances. Ensuring that your tyres remain legal is not about satisfying bureaucratic politicians or keeping the Police off your back; it is about keeping yourself, your passengers and other road users safe.
As of 1st November 2012 EU legislation came into effect that clearly showed how a particular tyre will perform since all tyres do not offer the same performance. This enables you to make an informed choice, balancing your budget with the benefits the tyre provides, ensuring that you can make the best decision possible when buying new tyres.
A
G
D
When a tyre rolls over the road it deforms and dissipates energy, mainly heat. The lost energy is known as rolling resistance and has a direct impact on fuel consumption. The difference in fuel consumption between a car fitted with A and G class tyres is around 0.5 litres per 100km. That makes a saving of around 80 litres and more than £110 per year. *
* Based on a petrol engine car travelling 10,000 miles per year with £1.40 per litre fuel cost.
Lower to higher fuel consumption
Not used
A tyre with excellent wet grip enable you to brake in a shorter distance on slippery roads. This is essential for keeping you safe in the rain. These ratings are measured from the distance travelled by a car after braking at 50mph in the wet. * There is a 30% shorter braking distance between the best and worst class of a full set of tyres fitted to an average car.
* Testing according to regulation
EC 1222/2009
D
Not used
Short to longer braking distance in wet conditions
G
A
G
+
Exterior noise levels are measured in decibels (dB) and shown as one, two or three sound waves on the label. One wave is the best performance, three is the worst. In fact, three bars is the current limit. Two bars on the label indicate that the tyre meets future European limits and one bar is a further 3 dB lower than that.
Note: External tyre rolling noise is NOT related to interior vehicle noise.
This legislation affects all new cars, 4x4's, SUV's, vans and most trucks and will appear in the form of a label stuck to the tyre when it is purchased, similar to the energy rating stickers that now appear on white goods.
The tyre label focuses on three areas of performance -:
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Fuel Efficiency - How economic is the tyre = Savings
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Wet Grip - How quickly can the tyre stop in wet conditions = Safety
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Exterior Noise - How noisy is the tyre = Sound
Tyres that are not affected by these regulations are racing tyres, professional off-road tyres, spare tyres, vintage tyres, re-treaded tyres, studded tyres and tyres whose rating is less than 80km/hr.
Rolling resistance is the force acting opposite to the direction of travel when a tyre is rolling. Due to the vehicle load, the tyre is deformed where the tyre makes contact with the road. This deformation induces internal losses in the same way that a rubber ball that is dropped does not bounce as high as it was originally dropped. The lesser the deformation the greater the fuel efficiency. Other factors that affect fuel consumption include -:
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Aerodynamics
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Vehicle weight
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Type of engine
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Auxiliary systems like air conditioning
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Slope of the road
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Personal driving style
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Tyre pressure level
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Accelerations
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General traffic conditions.
As a rule of thumb, reducing rolling resistance by 6% decreases fuel consumption by 1% for passenger cars.
The wet grip of a tyre refers to the safety performance as it reflects the capacity of a tyre to brake on a wet road. There are other factors which are relevant to safety such as -:
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Road holding ability
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Directional control
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Deceleration ability on wet and dry surfaces at higher speed
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Aquaplaning behaviour
