We're told, not necessarily reliably, what little girls and little boys are made of. Happily, we can learn with accuracy what car tyres are made of, and it's reassuring to know that the flexible friends that let our cars be steered and stopped unfailingly are so well constructed.
The heart of a car tyre is an inner liner made of halobutyl rubber. This includes additives that promote air retention. The inner liner is clad in a three-layer body ply, consisting of a layer of Rayon, Nylon, Polyester or Kevlar sandwiched between two layers of rubber. Car tyres may have one or two body plies, giving structural strength and flexibility.
We now move on to visible structures in our car tyre. Using materials that include antioxidants and antiozonants lets car tyre sidewalls resist abrasion and chemical attack, while promoting flexibility and strength.
The inner edges of the sidewalls are the car tyre's beads. Made of corrosion-resistant copper or brass-coated high tensile steel wire moulded into rubber casings, the beads are a strong point, holding the car tyre to the wheel and keeping air sealed inside. The triangular-section area joining the bead and the sidewall is the apex, the cushion between the two.
Back under the skin of the car tyre, beneath the tread, lies the belt package. Two layers of rubber sandwich a layer of steel cords. This package is what allows the car tyre to handle road impacts, from potholes, stones and so on. Usually the cords run radially within the belt package, hence the name 'radial tyre'. The visible tread and the layers beneath it are made of rubber compounds with a specific degree of hardness. Harder compounds wear well, softer compounds offer better grip; a compromise between the two is usually offered.
Now we know what car tyres are made of, how do we go about building one? In short, we don't, unless we happen to own a car tyre factory. In such a premises, a tyre's inner liner, body plies, sidewalls and beads are first assembled around a special drum. After the belt package and tread are added, the components are spliced together before the tyre is automatically inflated and shaped. At this stage, the tyre is uncured, or 'green'.
In this green form, the car tyre's parts are yet to be bonded together, in a curing process. A rubber bladder, inflated inside the car tyre with hot water, steam or an inert gas, forces it into a mould. The 350-degrees Fahrenheit temperature and 350psi pressure used speed up chemical reactions in the car tyre carcass, and the curing process takes about 15 minutes.
The cured car tyre is run on a mock tarmac surface, to highlight any localized inflexibility and/or unbalanced sections. While all tyres are visually inspected, a random sample of tyres is also X-rayed.
Heavy-duty equipment and extremes of pressure and temperature are used make a car tyre. It's comforting to know that these things combine to produce a tough, long lasting result.
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Merityre.co.uk are one of the leading UK independent suppliers of car tyres. Why not visit their website for an online tyre quote or contact your nearest fitting centre.
