In automotive braking systems, what internal construction feature of a ventilated disc brake rotor provides the most effective cooling during vehicle motion?

Introduction / Context:

Brake rotors convert kinetic energy into heat. Managing that heat prevents fade, pad glazing, and fluid boil. Ventilated discs are widely used on front axles because they enhance convective heat rejection without excessive mass increases.

Given Data / Assumptions:

• Passenger vehicle brake rotor with two rubbing faces and internal cavities.
• Vehicle airflow increases with speed, aiding cooling.
• Standard floating or fixed calipers with typical pads.

Concept / Approach:

A ventilated disc uses radial vanes sandwiched between the two rubbing surfaces to form internal air passages. As the rotor spins, it functions like a centrifugal pump, drawing cooler air from the center and expelling heated air at the periphery, greatly improving convective heat transfer.

Step-by-Step Solution:

Verification / Alternative check:

Thermal analyses and dynamometer tests consistently show ventilated vaned rotors reduce peak temperatures and fade versus solid rotors at equivalent mass.

Why Other Options Are Wrong:

• Many small holes: cross-drilling can help de-gas/wet performance but is not the core ventilated design and may reduce structural integrity.
• Duct to caliper: brake-cooling ducts assist but are ancillary and target the rotor more than the caliper body.
• Caliper fins: calipers benefit minimally; the rotor is the main heat sink.
• Thicker hub: adds mass but does not actively pump air through the friction ring.

Common Pitfalls:

• Confusing cross-drilled/slotted rotors with true ventilated radial-vaned rotors.

Final Answer:

disc contains radial vanes between its rubbing surfaces for optimum cooling performance