Primarily, a tyre consists of natural (30%) and synthetic (5%) Indian rubber and a lot of other materials like vulcaniser, tenderiser, steel wire and textile fibres, e.g., Polyester, Rayon, Kevlar or Aramid. Out of these basic substances the parts of a tyre are formed, partly in different factories.
First and foremost there is the processing of the steel-wire cords. Under almost antiseptic conditions the steel wires are coated with rubber in a calender and are then consolidated into a carass layer. The textile cords made from synthetic fibers e.g., Rayon, Nylon or Aramid go through the same process, however, in contrast to the steel belt, from beading to beading. The steel central ring (beading) with central tread is developed in a similar fashion.
A screw extrusion press produces - perhaps in another factory - the tread-strip, in principle, like an endless rubber band. After being checked for precisely constant weight, the band is cut to the final tyre size. Once again the side wall and inside layer which are made from air-tight, synthetic Indian rubber are similarly developed, this process replaces the inner-tube.
The wrapping represents the final assembly of the tyre-blank, with beading cores, inner core, cores of a harder mixture, steel belt and side walls. Finally the tread-strip is put on. The tyre has now very roughly its external form and size, but still no tread. It is sprayed with a special liquid and then placed in the round form where, from above only one segment is visible.
Two parts of the movable outside contour showing the negative form of the tread can be seen. They are moved over the guide pieces in the upper edge towards the centre so that a closed circle is formed. On top the same heated plate which is used under the form, is brought into position. At this point, from the inside, a part is used which completely seals the tubeless tyre almost like a wheel rim and then pumps in pressurized steam. In this way, the blank is pressed into all the indentations and is thus given its final form.
It is important to mention that due to the vulcanizing process, the single components are irrevocably bonded to each other. The treads have become so varied and the series often so small that tyre manufacturers frequently leave the production to specialized companies. Through the aluminium form, made using CNC technology, the tyre takes on the finest profiles from the given form. Mostly the form is more exact than would be necessary for the tyre production. Of course all parts can be exchanged, e.g., the rings bearing the tyre codes. 08/08