Brian Joss – As the physical link between a vehicle and the ground, tyres take on the full wheel load of a vehicle – when pulling off and braking they deliver the requisite grip, and when cornering they provide lateral guidance.
Tyres are developed for use on a wide range of surfaces, at different temperatures and with all kinds of loads.
Radial tyre construction, identified with an ‘R’ before the wheel rim diameter on the sidewall of the tyre, is used in all passenger car, light commercial and 4×4 tyres. The term ‘radial’ is derived from the structure of the layers in the casing of the tyre. These run radially, or 90-degrees to the tyre circumference. The layers of ply are known as the casing and consist of thin wires and fabric, arranged in a series of simple arches.
When it comes to choosing tyres, there’s simply no one-size-fits-all solution. Modern passenger car radial tyres are composed of up to 25 different structural parts, and as many as 12 different rubber compounds to suit the specific vehicle and intended use. The main structural elements are, firstly, the casing, which cushions the tyre and contains the required volume of air which carries the load of the vehicle (not the tyre). Secondly, the tread/belt assembly envelopes the casing and determines the tyre’s performance characteristics relating to rolling resistance, wet and dry braking performance, handling and mileage.
Within the Continental tyre range, there are dedicated products to suit every type of vehicle. In the case of compact cars or hybrid vehicles where the focus is on low emissions, fuel economy and reduced running costs, a tyre such as the EcoContact 6 is ideal. It features an innovative Green Chili tyre compound technology designed to provide low rolling resistance, improved fuel economy, reduced noise and high mileage.
The Continental PremiumContact 6, by comparison, is developed for larger, sportier vehicles where the priorities are maximum wet braking performance, a high level of ride comfort with low noise levels, along with precise cornering stability and control.
Continental’s range-topping SportContact 6 is an ultra-high-performance tyre developed for sportscars and supercars to deliver the ultimate grip and control at speeds of up to 350 km/h. It uses a special Black Chili compound, along with a unique Force vectoring tread pattern for maximum grip, and an Aralon 350 cap ply for exceptional high-speed stability.
Continental also produces a specialised range of tyres for the growing number of electric vehicles, which offer the lowest possible rolling resistance to achieve maximum energy efficiency and operating range.
Additionally, the company manufactures a range of Self-Supporting Runflat (SSR) tyres, which incorporate a reinforced sidewall to support the vehicle in the event of a loss of air pressure. This allows the driver to continue driving at a reduced maximum speed of 80 km/h for up to 80 km, ensuring that they aren’t stranded on the side of the road. SSR tyres may only be fitted on vehicles approved for runflat tyres, and that are equipped with a tyre pressure monitoring system.
All of these are summer tyres, designed for warmer temperatures and climates, as is the case in South Africa. They have a significantly firmer tread than winter tyres and offer far higher mileage and optimal rolling resistance. This is down to the tyre compound, which consists mainly of synthetic rubber.
Winter tyres are not recommended for use in South Africa. They are designed for markets where sustained, extremely cold temperatures with snow and ice are the norm. They incorporate specific rubber compounds optimised to provide grip at very low temperatures, along with extra sipes to improve the tyre’s ability to interlock with the road surface in slippery conditions. However, using these in South Africa’s typically hot driving conditions may lead to premature tyre wear and compromised driving safety.
Tyres designed for 4×4 and sport utility vehicles (SUV) vary greatly depending on application – from purely on-road driving for compact or performance-oriented SUVs, to all-round tyres for mixed on and off-road use, or extreme off-road tyres developed to handle the most punishing terrain.
Selection criteria include the anticipated proportion of on-road versus off-road driving and the associated tread design requirements. The ContiPremiumContact 5 SUV, for example, is designed purely for on-road use with superb grip and braking performance.
The ContiCrossContact LX and LX Sport are suited to light off-road and gravel driving conditions, with ratios of 80/20 and 90/10 respectively, while the CrossContact ATR features a more rugged construction and tread pattern, and a 70/30 ratio for more demanding applications.
The ContiCrossContact AT is Continental’s versatile and very capable all-round 4×4 tyre, developed for an equal mix of on-road and off-road use. It is a popular fitment in the original equipment market for double cab pickups in South Africa.
CAPTION: Nice takkies: the Mercedes is shod with the Continental Sport Contact. Picture: Quickpiv