Automotive tyres — bead construction Bead wires, which anchor the tyre to the rim and maintain shape under pressure, are typically made from which material?

Introduction / Context:
The tyre bead forms the interface between tyre and rim, securing the tyre under internal pressure, cornering, and braking forces. The bead must be strong, fatigue-resistant, and dimensionally stable.

Given Data / Assumptions:

• Pneumatic tyre with rubber compound, cord plies, bead fillers, and bead wire(s).
• Operating pressures and loads typical of passenger or commercial vehicles.
• Rim hardness and geometry per standards (e.g., bead seat taper).

Concept / Approach:
High-tensile steel wire (often copper- or brass-plated for adhesion) is used for beads because it provides superior tensile strength, stiffness, and durability in a compact cross-section. The wire is wound into hoops, embedded in rubber, and works with bead fillers to maintain sealing and retention.

Step-by-Step Solution:
Identify the function: resist hoop stress and maintain airtight seal.Match material to requirement: high tensile strength and fatigue resistance → steel.Therefore, bead wire material is steel.

Verification / Alternative check:
Cutaway tyres and manufacturer datasheets specify steel bead bundles; metal detectors also reveal steel at the bead.

Why Other Options Are Wrong:
Copper, zinc, and aluminium lack the required combination of tensile strength and cost-effectiveness for bead cores.

Nylon is used in plies or cap plies but not as bead wire.

Common Pitfalls:
Confusing bead wire with reinforcement cords; cords can be polyester, nylon, steel, or aramid, but bead cores remain steel for most applications.

Final Answer:
steel