The tyre is part of the tyre and wheel system and its job is to transmit the forces between the car and the road.
The tyre is the only direct link between the car and the road. The tread contact area must support the weight of the car and must be able to transmit both longitudinal and lateral forces:
In addition, the tyres must also satisfy the following requirements:
The tyres thus have a crucial influence on handling, safety and the comfort of a vehicle.
On average, a modern car tyre contains up to 25 components and 12 different rubber compounds. These include:
These components vary depending on the tyre size and type (for example summer tyres, winter tyres).
Tyres are manufactured using a complex production process, which ends with the process known as “vulcanisation”. This involves heating the green tyre under pressure at temperatures of up to 200°.
A tyre is not a homogeneous piece of rubber; it has a sophisticated construction.
The tyre profile is hugely important. The tread profile of a tyre is its link to the road. The profile pattern has a critical impact on factors such as grip and vehicle handling.
Every tread profile is made up of four components:
The ribs, grooves, tread blocks and sipes can be arranged in particular patterns to optimise the performance of the tyre in terms of noise generation, handling, traction and wear. This enables tyre manufacturers to develop profile patterns tailored for specific driving requirements such as braking in the wet, handling on dry roads, resistance to aquaplaning and traction on ice and snow.
The tread and thus the profile is subject to natural wear. The tread depth reduces over the service life. A tyre is classed as worn and no longer roadworthy if it has less than the specified minimum tread depth of 1.6 mm.
Signs of wear - known as tread wear indicators (TWIs) - are wear indicators integrated into the tyres. They are uniformly distributed ridges in the longitudinal grooves all around the tyre. If they can be clearly identified and at the same height as the rest of the tread, the tyres need to be replaced.
A basic distinction is made between summer tyres, winter tyres and all-weather tyres:
Tyres are also differentiated according to the position of the cord plies: On radial tyres, the cord plies in the carcass are at a 90 degree angle to the direction of movement. For cars, radial tyres - also known as belt tyres - have completely superseded cross-ply tyres.
All tyres sold in the European Union must have a prescribed tyre marking. The EU tyre label provides specific information about a tyre’s environmental and safety properties taking into account the three following criteria: Fuel efficiency, wet braking properties and noise level.
The fuel efficiency of a tyre depends on its rolling resistance. It is rated using the classes A (highest fuel efficiency) to G (lowest fuel efficiency). From one class to the next, the fuel consumption increases by around 0.1 litres per 100 kilometres.
A tyre’s wet braking properties are crucial for safe driving on a wet road. Wet grip describes a tyre’s performance in the wet and is also split into classes A to G. In general, the EU label is based on a speed of 80 kilometres per hour. If a vehicle brakes at this speed in wet conditions, a class A tyre comes to a standstill after 28 metres. By contrast, a class F tyre comes to a standstill after 46.5 metres. As a result, there are more than 18 metres between these two classes
The noise level relates to the tyre’s external rolling noise. It is measured in decibels. The lowest sound level is between 67 and 71 dB. The highest level is between 72 and 76 dB.
The tyre is an extremely safety critical component. As a result, tyres should be checked and maintained regularly to guarantee continuing safety on the road.
Careful handling and regular checking and maintenance contribute to value retention. Drivers should regularly check the air pressure, avoid bumping into kerbs and always have new tyres balanced by a specialist dealer.
The well-known manufacturers place considerable value on protecting the environment. They go to considerable lengths to make their tyres more energy efficient and environmentally friendly.
Disposal of used tyres in landfill is illegal in the European Union and other countries. Many tyre dealers offer disposal of used tyres for their customers when they buy new tyres.