Rolling Resistance vs. Aerodynamic Drag (2D)

Drive Settings

Vehicle speed 60 km/h

Vehicle mass (load) 1500 kg

Tire pressure 2.2 bar

Road Surface

Live Energy Budget

■ RollingDrag ■

Rolling resistance F_rr

— N

Aerodynamic drag F_d

— N

Power required to sustain speed

— kW

Crossover speed (F_rr = F_d)

— km/h

How it works

A cruising vehicle fights two resistive forces at once. Rolling resistance comes from tire deformation at the contact patch and barely depends on speed:

F_rr = C_rr · m · g

Aerodynamic drag comes from pushing air out of the way and grows with the square of speed:

F_d = ½ · ρ · C_d · A · v²
ρ = 1.225 kg/m³ (air), C_d = 0.30, A = 2.2 m²

Total power to hold a steady speed is P = (F_rr + F_d) · v. At low speed rolling resistance dominates the energy bill; because drag scales with v² it always overtakes rolling resistance above a crossover speed:

v_cross = √( F_rr / (½ρC_dA) )

Higher tire pressure shrinks the contact patch and lowers C_rr (modeled here as C_rr ∝ 1/√pressure); softer surfaces like gravel or sand raise the baseline C_rr by letting the tire sink in and deform more. The bottom panel plots both forces against speed as continuous curves — drag the graph to scrub the vehicle to any speed and watch the two curves cross exactly where the stat box above says they should.

drag road: pan camera · drag graph: scrub speed