Rolling resistance in road vehicles Rolling resistance primarily arises due to friction and deformation between which two elements?
Correct Answer: tyre and the road surface
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:
Identify the contact: tyre tread meets the road; deformation occurs as the patch enters and leaves contact.Account for viscoelastic losses in rubber compounds contributing to resistance.Conclude that the principal interface is tyre–road, not tyre–rim or rim–road.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:
tyre and the road surface