The first practical pneumatic tire was made by John Boyd Dunlop, born in Scotland, while working as a veterinarian in May Street, Belfast, in 1887 for his son's bicycle, in an effort to prevent the headaches his son had while riding on rough roads (Dunlop's patent was later declared invalid because of prior art by fellow Scot Robert William Thomson). Dunlop is credited with "realizing rubber could withstand the wear and tear of being a tire while retaining its resilience".
Pneumatic tires are made of a flexible elastomer material, such as rubber, with reinforcing materials such as fabric and wire. Tire companies were first started in the early 20th century, and grew in tandem with the auto industry.
Racing tires are highly specialized according to vehicle and race track conditions. This classification includes tires for drag racing, drifting, Road Racing – as well as the large-market race tires for Formula One, IndyCar, NASCAR, rallying, MotoGP and the like. Tires are specially engineered for specific race tracks according to surface conditions, cornering loads, and track temperature. Racing tires often are engineered to minimum weight targets, so tires for a 500-mile race may run only 100 miles before a tire change, or 300 Km Formula 1 race may run only 150 Km. Some tire makers invest heavily in race tire development as part of the company's marketing strategy and a means of advertising to attract customers.
Racing tires often are not legal for normal highway use.
In Formula 1, the type of rubber mix used in the construction of a tire, ranging trough four different compounds from supersoft, soft, to hard and extra hard with each offering a different performance and wear characteristic.
Before, in time of two tire suppliers (Goodyear - Bridgestone, Bridgestone - Michelin), number of compounds are not limited on four types only. During tire manufacturer "war", compounds are mixed specially for each circuit. And not only one of them. There were always few choices driver can make with help of racing engineer depending of track temperature and track quality.
FIA introduced rule with only one supplier and only 4 different compounds to be used during the year. Manufacturer has to announce few month before race what type of rubber will be available to the team during certain race.
FIA introduced "One supplier rule" because tires start to became so competitive and compounds so sophisticated and with so strong grip that car speed during cornering and breaking start to be to dangerous. Cars where like glued to track, but ones grip is lost because of any reason, it was almost impossible to control the spin. Other reason to go with only one supplier was cost cutting. Price of development of those tires was so high.
The tire is an assembly of numerous components that are built up on a drum layer by layer and then cured in a press under heat and pressure. Heat facilitates a polymerization reaction that cross links rubber monomers to create long elastic molecules. These polymers create the elastic quality that permits the tire to be compressed in the area where the tire contacts the road surface and spring back to its original shape under high-frequency cycles. Typical components used in tire assembly are:
- Natural rubber, or polyisoprene is the basic elastomer used in tire making
- Styrene-butadiene co-polymer (SBR) is a synthetic rubber which is often substituted in part for natural rubber based on the comparative raw materials cost
- Polybutadiene is used in combination with other rubbers because of its low heat-buildup properties
- Bromobuty rubber is used for the tubeless inner liner compounds, because of its low air permeability. The halogen atoms provide a bond with the carcass compounds which are mainly natural rubber. Bromobutyl is superior to chlorobutyl, but is more expensive
- Carbon Black, forms a high percentage of the rubber compound. This gives reinforcement and abrasion resistance
- Silica, used together with carbon black in high performance tires, as a low heat build up reinforcement
- Sulphur cross links the rubber molecules in the vulcanization process
- Vulcanizing Accelerators are complex organic compounds that speed up the vulcanization
- Activators assist the vulcanization. The main one is zinc oxide
- Antioxidants and antiozonants prevent sidewall cracking due to the action of sunlight and ozone
- Textile fabric (mainly Kevlar and carbon fyber threads in Formula 1) reinforces the carcass of the tire
Compounding is the operation of bringing together all the ingredients required to mix a batch of rubber compound. Each component has a different mix of ingredients according to the properties required for that component.
One of the most important parameters of a given rubber compound reinforced with Carbon Black is the micro dispersion of the filler. This micro dispersion governs the
fundamental viscoelastic response of the compound and is responsible for a ratio of the tiller-filier to polymer-filler interactions. The balance between these two types of interactions is dictating the most relevant properties of the finished tire.
The first classical law of friction states: “The size of the contact surface does not influence the friction”. Why, then, are tires for the Formula 1 racing cars so wide?
According to the “FIA Technical Commission”, the organization that decides on the technical rules for Formula 1, the front and rear tires should not be wider than stated in technical regulation.
The classical friction laws apply to materials that undergo mainly plastic deformation in the asperity summits. This in not the case for polymers (and elastomers). Polymers display a lower friction coefficient at higher nominal contact pressure (narrow tires - higher nominal contact pressure and vice versa). A high friction force can consequently only be achieved with a large surface area.
Other advantages of a wide surface are that the wear is distributed over a larger area, heat development per unit of surface is lower and the result is a larger heat-radiating surface.