The third-degree test for tyres
The tyres fitted to our vehicles undergo numerous tests before they are put into production. They are analysed under all conditions: on the track, on the road and then are given the third-degree by sophisticated machines. Their propertiees are examined, whether rolling resistance, noise, grip, wear, etc, … A brief detailed overview.
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This measures the capacity to withstand load and overload over time, whatever the weather conditions. The tests reproduce ordinary and abnormal driving situations. The tests are also carried out on machines on which the tyres are ripped apart in order to fine-tune the study of the damaged part. This enables samples of the rubber comprising the tyre to be examined by the laboratory chemical experts.
Rolling resistance test
- Fuel consumption at a stabilised speed: 2 identical vehicles fitted with tyres with a different rolling resistance drive at the same speed. It can be seen that a lower rolling resistance generates a reduction in fuel consumption.
- Rolling resistance may be measured on a machine which reproduces the tyre use conditions and takes into account the load and pressure. The machine drives the tyres and measures the load necessary to keep it rotating, and this load, is the rolling resistance load.
These tests analyse the capacity of the tread to resist wear and therefore measure the tyre potential lifespan. They are conducted in a real-life situation using identical vehicles which continually eat up the kilometres on the roads in France. After several thousand kilometres, the prototypes are recovered, cleaned, and their rubber is measured and recorded. The performances of the technical options are then simply analysed, and compared and validated. For practical and economic reasons, this type of test is often carried out on machines which closely reproduce the road characteristics.
Noise and comfort tests
These are conducted on the track or off the track and on almost all types of surfaces. On a macro-roughness surface which enables testing of interior noise and the global comfort of the vehicle. Then we switch to a smooth surface which more emphasises the noise from the tyre tread and which is measured using specific apparatus. We can also place obstacles on the road (metal bars) which enable us to check if the tyre can easily handle sharp edges. And then, thanks to test tracks fitted with trackside sensors, the exterior noise and nuisance generated for the neighbourhood will be analysed. The performances must comply with legislation criteria.
Braking and grip test
Firstly, the longitudinal grip is measured and determines the capacity of a vehicle and its tyres to decelerate under emergency braking in a straight line. In this case, a vehicle is driven along a dry or wet track and then undergoes emergency braking. The distance covered by the vehicle under braking measures the performance of the tyre-vehicle configuration tested. Then we measure the lateral grip which represents the capacity of the vehicle to follow a circular trajectory on a wet surface. The vehicle is then studied under limit grip conditions. Aqua-planing situations (7 mm deep puddle) are also analysed in order to determine the capacity of the car to hold its line. After these tests, the manufacturers can decide on the final assembly of the semi-finished products which will constitute the tyre in its final form. The same tests may be carried out on worn tyres in order to examine the alteration in their performance.
This involves safety and driving comfort and measures the response given by the vehicle and the tyres under braking, acceleration or steering stresses. The tests are conducted on dry surfaces (for all driving conditions) and wet surfaces (various wetting conditions). All this is combined with the driver feedback and information provided by the on-board measurement instruments.
These tests are common to the most well-known manufacturers on the tyre market. There is no compulsory legislation to so exhaustively test tyres, or in any case, until 2012. In effect, the European Parliament has validated a new compulsory labelling system. It introduces three interesting rating criteria, covering fuel savings, wet surface grip and noise level.
Not all manufacturers have such sophisticated test centres such as Ladoux for Michelin or that of Bridgestone, near Rome. The more « exotic » manufacturers on the tyre market do not carry out such a wide range of tests, which are too expensive and require an in-depth knowledge of the product. However, the tyres they put onto the market meet with the legislatory standards. It can nevertheless be seen that the development research of the so-called Premium manufacturers bears fruit as they are very often those most rated or praised by consumers or independent test bodies.
These tests are only the visible part of the marketing process of a new tyre. A tyre is composed of almost 250 semi-finished products and they are all subjected to specific analyses, not only as a single entity, but also as a tyre component.