2. What is the Tire’s Rolling Resistance?
Rolling resistance is one of the resistive
forces acting on a vehicle: aerodynamic drag
inertia internal friction
gravity
rolling resistance
α = road slope
* WBCSD – Mobility 2030 Full Report - 2004
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3. What is the Tire’s Rolling Resistance?
A rubber ball does not rebound as high as it was
launched. Indeed at each rebound, the ball is
deformed and hence energy is dissipated.
The same way, when a tire rolls, it is deformed
and it dissipates energy. The energy dissipated
by the tire is the tire’s rolling resistance.
Rolling resistance contributes circa 20% to the
car’s fuel consumption.
Less Rolling Resistance = Less Fuel Consumption
= Less CO2 Emissions
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4. Tire’s Rolling Resistance Classes.
C1 Rolling Resistance C2 Rolling Resistance
classes classes
RRC≤6.5 A RRC≤5.5 A
6.6≤RRC≤7.7 B 5.6≤RRC≤6.7 B
7.8≤RRC≤9.0 C 6.8≤RRC≤8.0 C
Empty D Empty D
9.1≤RRC≤10.5 E 8.1≤RRC≤9.2 E
10.6≤RRC≤12.0 F 9.3≤RRC≤10.5 F
RRC≥12.1 G RRC≥10.6 G
C3 Rolling Resistance
classes
RRC≤4.0 A
4.1≤RRC≤5.0 B
5.1≤RRC≤6.0 C Method for Rolling Resistance
6.1≤RRC≤7.0 D laboratory alignment still to get
final approval, expected in
7.1≤RRC≤8.0 E November 2011.
RRC ≥8.1 F
Empty G
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5. How is Rolling Resistance Measured ?
Rolling resistance is measured
in a lab on a large drum
Many factors influence the tires
rolling resistance, e.g.:
Vehicle weight
Driving style
Tire inflation pressure
Type of tire and materials
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7. Are under-inflated tires a common problem?
Research results:
Studies carried out by the European
Union have shown that more than 64% of
all cars have under-inflated tires.
Goodyear Dunlop 2010 Road Safety
Survey confirms that drivers don’t check
their tire pressure regularly.
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8. European drivers’ perceptions
73% of EU respondents claim to know the appropriate tire pressure for different
driving conditions, but almost half of the people surveyed didn’t know when
exactly to check tire pressure (when the tires are cold).
While 59% of respondents stated they regularly checked their tire pressure, half
of them admitted they might set out on a long journey without doing so.
52% say they regularly check their tires tread depth, but three in ten of them
can’t even remember the last time they did.
So there is a discrepancy between what motorists say they do and what they
actually do.
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9. What are the effects of incorrectly inflated tires?
Feel the effect yourself:
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10. What are the effects of incorrectly inflated tires?
Driving with under-inflated tires:
Reduces wet grip and aquaplaning resistance
Increases stopping distances
Reduces the car’s handling performance, esp. during cornering
Decreases high speed stability
Causes uneven tread wear with strong shoulder wear reducing tire
mileage
Increases rolling resistance and fuel consumption
Driving with over-inflated tires is less common but has similar negative
effects on the car’s grip and handling performance.
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11. What do we want to achieve?
We want drivers to:
Know the consequences of driving with
incorrectly inflated tires.
Know how to check their tire pressure.
Know the correct tire pressure according to
the car’s manual.
Check their tire pressure regularly, at least
once a month and prior to any long journey.
Adjust the tire pressure depending on the
vehicle’s load. If the vehicle is fully loaded, the
tire pressure must be increased according to
the car’s manual.
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12. What can you experience in this workshop?
Rolling Resistance
Coast Down Demo
Demonstration:
Rolling Resistance Demonstration:
Car with High-Grade tires in Rolling Resistance
against
Car with Low-Grade tires in Rolling Resistance
The choice of tires can have a major effect on the
car’s fuel consumption
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