The lower bead area.
Its role is to transmit engine and braking torque from the rim of the tyre through to the contact patch.
The bead wires
help to hold the tyre onto the rim. They can take a load of up to 1800 kg without the risk of breakage.
Supple rubber sidewalls
help to protect the tyre from shocks that could damage the casing, eg minor shocks against pavements, potholes etc. There is hard, protection rubber where the tyre joins the rim.
Reinforced with very fine, very resistant steel cords in a rubber sandwich. Two, (occasionally more), plies are stuck together and cross the tread area at angles of around 60? to each other. Their steel cords cross the casing cords to form braced triangles. This is known as triangulation, and it makes the crown rigid.
The plies encircle the entire crown of the tyre, and perform a very complex role: they must be sufficiently rigid around the tyre's circumference that they aren't stretched by the tyres rotation, must take the stresses and strains of cornering. At the same time, they must be supple enough to “absorb” bumps in the road.
To obtain these plies, steel has to be stuck to rubber. It is very difficult to do, Michelin pioneered the method of sticking these dissimilar materials, which is absolutely essential.
is laid over the bracing plies. It is the patterned part of the tyre that will be in contact with the road. The tread in the contact patch must be able to resist very significant stresses. The tread rubber compound must grip on all types of surfaces, resist wear and abrasion, and heat up as little as possible. All that then remains is to mould in the tread pattern and vulcanize all these semi-finished products together to form what we know as a whole tyre.