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Workshop Rolling Resistance

Welcome

Stefan Köppen Tire Test EngineerGoodyear Innovation Center Luxembourg

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What is the Tire’s Rolling Resistance?

Rolling resistance is one of the resistive forces acting on a vehicle: aerodynamic drag

α = road slope

internal frictioninertia

rolling resistance

gravity

* WBCSD – Mobility 2030 Full Report - 2004

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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 CO 2 Emissions

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Tire’s Rolling Resistance Classes.C2 Rolling Resistance

classesRRC≤5.5 A5.6≤RRC≤6.7 B6.8≤RRC≤8.0 CEmpty D8.1≤RRC≤9.2 E9.3≤RRC≤10.5 FRRC≥10.6 G

C1 Rolling Resistance classes

RRC≤6.5 A6.6≤RRC≤7.7 B7.8≤RRC≤9.0 CEmpty D9.1≤RRC≤10.5 E10.6≤RRC≤12.0 FRRC≥12.1 G

C3 Rolling Resistance classes

RRC≤4.0 A4.1≤RRC≤5.0 B5.1≤RRC≤6.0 C6.1≤RRC≤7.0 D7.1≤RRC≤8.0 ERRC ≥8.1 FEmpty G

Method for Rolling Resistance laboratory alignment still to get final approval, expected in November 2011.

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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 weightDriving style Tire inflation pressureType of tire and materials

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Video: How is Rolling Resistance Measured ?

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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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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 chec ked their tire pressure, half of them admitted they might set out on a long journ ey without doing so.

52% say they regularly check their tires tread dept h, 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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What are the effects of incorrectly inflated tires?

Feel the effect yourself:

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What are the effects of incorrectly inflated tires?

Driving with under-inflated tires:Reduces wet grip and aquaplaning resistanceIncreases stopping distances Reduces the car’s handling performance, esp. during corneringDecreases high speed stabilityCauses uneven tread wear with strong shoulder wear reducing tiremileageIncreases 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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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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Rolling Resistance Coast Down DemoDemonstration:

Rolling Resistance Demonstration:Car with High-Grade tires in Rolling Resistance againstCar with Low-Grade tires in Rolling Resistance

�The choice of tires can have a major effect on the car’s fuel consumption

What can you experience in this workshop?