1. Tires
A tire is a composite material which has rotational symmetry, is non-isotropic, and is comprised of several rubber components which are bound together, and whose strength characteristics are determined by textile or other steel reinforcement materials. This is the formal definition of a tire as given by an encyclopedia.
A tire is tasked with far more than just supporting the weight of a vehicle. It should be able to apply lateral forces to guide the vehicle safely along curves and apply longitudinal forces to transfer engine power and brake forces onto the road. It should offer maximum possible adhesion to road surfaces under all weather conditions, have spring and damping properties, be able to support steering inputs through suitable response characteristics, and have a minimal amount of rolling resistance and road noise. With regard to longevity and durability, a tire should be able to endure considerable amounts of mileage, be as air-tight as possible, and be suitably robust against external influences. Lastly and most importantly, a tire must be safe: it should retain its specified dimensions over its lifecycle and should not become detached from the wheel rim while the vehicle is in motion.
Unfortunately, the properties listed above are not exactly free from conflict. Therefore, an optimal compromise must be reached during the development of new tires. Determining this optimal compromise becomes the task of vehicle manufacturers, while the technical implementation becomes the task of tire manufacturers [1, 2].
Modern passenger cars use steel-belted radial tires almost exclusively. Steel-belted radial tires from different tire manufacturers have few significant differences from one another, Fig..
Fig. 1.1
History of tire outside diameter for the Mercedes S-Class
The core profile is located above the tire bead cable and is made of synthetic rubber. The core profile influences the vertical spring stiffness and hence the comfort aspect of a tire. The core profile, like the bead reinforcement, which is made of nylon or aramid, also ensures the precision of steering and dynamic stability while driving.
The sidewall rubber is made of natural or synthetic rubber and protects the tire carcass against lateral damage and weathering. The rubberized polyester- or rayon-finished textile cord carcass is essentially the reinforcing material against the tires internal air pressure.
The steel cord-belt inserts are made of rubberized steel cord and help to ensure stability while driving, help to reduce rolling resistance , and increase tire mileage. The joint-less bandage made of nylon improves high-speed capabilities.
A steel-belted radial tire can be made from more than twenty different rubber mixtures. One important descriptive parameter for rubber mixtures, especially for the tire tread, is the shore hardness . Shore hardness can vary depending on the type of carbon black used and its proportion to the softening agent (plasticizer) as well as the dosing of the vulcanizing agent.
The belt from which a steel-belted radial tire earns its name consists of at least two steel cord-belt inserts. These are laid one above the other, are made of drilled or twisted steel wires, and are partly coated with brass. The belt is located below the tread and is covered by the nylon bandages. The steel wires do not run in the direction of the tread, but rather at a defined angle relative to the tread. On the sides, the belt inserts are either folded or cut.
The tire carcass consists of one or more radial layers of synthetic fibers or rayon. The sidewall serves as protection against damage to the carcass yarns (e.g. while driving over curbstones) and has a major impact on driving properties as well as passenger comfort. The properties of the sidewall vary depending on the nature of the material used as well as the geometry of the tire.
The tire carcass is surrounded by the tires shoulders and is largely responsible for driving characteristics. It consists of a mixture of elastomers, filler materials, oils, anti-aging materials, and vulcanizing agents. A large percentage of natural rubber in this mixture helps to reduce heat generation in the tread region. Synthetic rubbers, on the other hand, offer increased wear resistance (mileage) and grip . Carbon black and silica are the main filler materials used for a tires tread and help to increase wear resistance while at the same time stiffening the tread. Diluting oils serve to increase the workability of the mixtures. Anti-aging materials aim to prevent damage due to ozone. Vulcanizing agentslargely sulfur, but also stearic acid and zinc oxidepromote the binding activities during the vulcanization process. Another important feature of the tread is the tread profile , which largely determines noise properties as well as tire responsiveness under winter conditions, including aquaplaning and wet grip performance.
A variety of information is available on the sidewall, Fig.. This information includes the width of the tire , its cross-section measurement, tire design type, and rim size . The width is measured in millimeters, whereas the tire cross-section denotes the ratio of the height of the sidewall to the width of the tread. Modern passenger cars use tires with an R designation, for radial, meaning that the cord inserts run radially from tire bead to tire bead. In other words, they lie at an angle of 90 relative to the running direction of the tire. Rim diameter is described in inches.
Fig. 1.2
Tire markings
( Source Michelin)
The United States Department of Transportation (DOT) demands that details regarding a tires structure be written on the sidewall in the form of numerical codes. Normally, the term DOT Number refers to a tires date of manufacture, which is written in code form on the sidewall. For tires manufactured after 2000, the week of manufacture and the tire model appear as the last four digits of the code number.
The Uniform Tire Quality Grading (UTQG) classification is a sidewall marking prescribed by consumer ordinances in the United States which contains details about the operational performance (mileage or treadwear ), traction, and temperature.
Tires should have profile grooves around the entire tread periphery. Profile depth should be measured in the main grooves, which is additionally marked with tread wear indicators (TWI) in the case of modern tires.
A comprehensive overview of tire markings is given, for instance, in [3, 4] and on the websites of tire manufacturers. The most important information is also usually found in the user manual provided with new vehicles.
1.1 Tire Manufacturing
Tire manufacturers are independently responsible for the manufacturing of tires; however, automobile manufacturers must be familiar with tire manufacturers processes, techniques, and facilities [2]. In fact, tire manufacturing plants should be audited and approved by vehicle manufacturers. The basic processes of tire manufacturing are depicted in Figs..
