Making a tyre
From blending to inspection
Raw materials including pigments, chemicals, and up to 30 different kinds of rubber are mixed in giant blenders called Banbury machines, operating under tremendous heat and pressure. They blend the many ingredients together into a black, gummy compound that will be milled again and again.
The cooled rubber is processed into slabs that are transported to breakdown mills. These mills prepare the different compounds for the feed mills, where they are slit into strips to become sidewalls, treads or other parts of the tire. Still another kind of rubber coats the fabric that will be used to make up the tire's body. Many kinds of fabrics are used: polyester, rayon or nylon.
Another component, shaped like a hoop, is called a bead. It will fit against the vehicle's wheel rim.
Next come two layers of ply fabric, the cords. Next, a pair of chafer strips is added, so called because they resist chafing from the wheel rim when mounted on a car.
Now the tire builder adds the steel belts that resist punctures and hold the tread firmly against the road. The tread is the last part to go on the tire. After automatic rollers press all the parts firmly together, the tire, now called a green tire, is ready for curing and inspection.
The curing press gives the tires their final shape and tread pattern. Hot moulds shape and vulcanize the tire. The moulds contain the tread pattern, the sidewall markings of the manufacturer and those required by law. Tires are cured at over 300 degrees for 12 to 25 minutes, depending on their size.
If anything is wrong with the tire – if anything even seems to be wrong with the tire, even the slightest blemish - it is rejected. Some flaws are caught by an inspector's trained eyes and hands; others are found by specialized machines. Inspection doesn't stop at the surface. Some tires are pulled from the production line and X-rayed to detect any hidden weaknesses or internal failures. In addition, quality control engineers regularly cut apart randomly chosen tires and study every detail of their construction that affects performance, ride or safety.