Rolling resistance in road vehicles Rolling resistance primarily arises due to friction and deformation between which two elements?

Introduction / Context:
Rolling resistance is the parasitic force opposing motion that must be overcome by the powertrain. It affects fuel economy, range (in EVs), and performance.

Given Data / Assumptions:

• Pneumatic tyres on typical paved roads.
• Steady speed; aerodynamic drag considered separately.
• Tyre is inflated to a normal service pressure.

Concept / Approach:
Rolling resistance mainly results from hysteresis losses inside the tyre as it deforms in the contact patch, plus micro-slippage and friction at the tyre–road interface. The energy dissipated manifests as heat. Bearing and drivetrain losses exist but are not termed rolling resistance in the classical sense.

Step-by-Step Solution:

Verification / Alternative check:
Laboratory coastdown tests and drum dynamometer measurements attribute most rolling losses to tyre deformation and tyre–road frictional effects.

Why Other Options Are Wrong:

• Wheel rim–tyre: internal to the wheel and not the source of road rolling losses.
• Wheel rim–road: the rim does not contact the road during normal operation.
• Bearings only: contribute to mechanical drag, but rolling resistance refers chiefly to tyre–road effects.

Common Pitfalls:
Confusing aerodynamic drag with rolling resistance; neglecting the effect of inflation pressure and tyre construction on rolling resistance coefficient.

Final Answer: