Tire Technology Explained - Mysteries Of The Black Rubber Doughnut

A.) Bead Bundle
The foundation that anchors the inflated tire to the rim is the bead. It's easily the most rigidly circular portion of a tire. An individual bronze plated bead wire is immersed and coated with rubber (also called calandering) and then wrapped several times into a bundle of specific configuration and diameter. Depending on the applications, beads can be a bundle of small gauge wires, wound wires, or large solid core wires.

B.) Bead Filler or Apex
Attached to the top of the bead bundles is a triangular extrusion of harder rubber that fills the void created by the inner body plies and up turned body ply ends that wrap around the bead on the outside of the carcass. Varying the hardness (or durameter) and height of this filler can affect tire performance characteristics.

C.) Abrasion Gum Strip or Chaffer
This hard rubber strip acts as a protective layer between the body plies and the rim to prevent chaffing. Under extreme conditions, tires might actually rotate slightly on the wheel itself or deform side to side causing the rubber to abrade against the wheel.

D.) Sidewall
The sidewall rubber serves to protect the body plies from cutting, abrasion, impact, and flex fatigue. The rubber compound is formulated to resist cracking due to environmental conditions such as ozone, heat, UV radiation, and oxygen.

E.) Sidewall Reinforcements
Some tires have sidewall reinforcements added to improve the stability and handling characteristics of the tire. These items are known as flippers, chippers, or a floating reinforcement. Run flats usually have thicker sidewalls and other reinforcements to help protect the tire by supporting the load in the event of under inflation.

By Samuel Kwa

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