EU Tyre Label: How the tyres are tested
Since June 2012, tyre manufacturers have been required to provide data in relation to the performance of their tyres through testing.
Due to the sheer vast number of tyre models, it was decided that a centralised EU tyre testing facility would be unmanageable and unproductive. Therefore, tyre label testing is self-certified using specific EU standardised methods that every test must adhere to.
Testing Rolling Resistance
A tyre is mounted to a specially designed two-metre drum. It is then rotated with a defined load and pressure.
The test engineers have the torque required to rotate the drum before the tyre is fitted, so they are able to calculate the torque of the tyre by subtracting the new level required when the tyre is mounted against the level when it is not.
It is through calculating the difference of the drum's torque with or without the tyre that they can record what is known as the 'Rolling Resistance Coefficient'. This is what is used to work out the correct grading for the new tyre label.
Testing Wet Grip
There are two tests that engineers are required to carry out to come up with the wet grip rating.
First of all they need to carry out a wet braking test. This measures the performance of a tyre when a vehicle is braking on a wet surface. The distance that the car travels when slowing from 50mph to 12mph is recorded.
They also carry out what is known as a skid trailer test. This calculates the friction between the tyre and the road surface. For the tests to be valid, it must take place when the vehicle is travelling at 40mph.
Once they have both results, they combine them to create the Wet Grip Index (WGI) - this shows the percentage of improved ability compared with an independent reference tyre.
Testing Noise Emission
This test is done to find out the external noise of a tyre in decibels (dB).
The actual test consists of a microphone being set up on the edge of a track to measure the sound level of a test vehicle - the mircophone is required to be 7.5m from the centre of the track at sit at 1.2m above the ground. When passing, the vehicle must be travelling at 50 mph with the engine turned off for the test to be valid.