7/29/2019 Rolling Resistance Explained

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FUEL FAQS

1Fuel FAQs/1st Quarter 2012Visit us online at BridgestoneTruckTires.com. 2012, Bridgestone Americas Tire Operations, LLC. All rights reserved.

If you think about rolling a tire across the shop floor,

it will take effort to move it and even more effort if its

carrying a heavier load. Thats rolling resistance.

Where does rolling resistance come from?

As a tire rolls under a load, it deforms. It has to. The

load presses down on the tire and squashes it against the

road. As the tire turns, the squashed part comes off the

road and returns to its original shape while another part of

the tire gets squashed.

The sidewalls of the tire flex over and over again, close

to 500 times per minute at highway speeds. And, the tread

goes from a circular to a flat shape and back to circular

again.

Some of the energy that deforms the tire turns into heat

Tires and treads heat up as a result of rolling under load

sometimes quite a lot. This heat is lost. It does nothing to

help move the truck down the road. It is the source of what

we call rolling resistance.

How can we reduce rolling resistance?

Anything that reduces the deformation of the tire

will reduce heat loss and therefore, rolling resistance. A

solid iron tire would deform less, and have lower rolling

resistance. But even solid steel railroad wheels deform

somewhat and get quite warm. Besides, iron tires on

trucks wouldnt be very good for either our roads or the

cargoes we carry.

If we could figure out a way to avoid producing heat

when a tire is deformed, that would help reduce rolling

resistance.

SIDEWALLS FLEX

CIRCULAR TO FLAT FOOTPRINT

Tires deform as they roll. Sidewalls

flex, and treads go from circular tofla

as they enter and leave the footprint. Al

of these deformations create heat loss

that contribute to rolling resistance.

WHAT IS

ROLLINGRESISTANCE?ROLLINGRESISTANCE, SIMPLYPUT, ISTHEFORCEYOUMUSTEXERTTOROLLA

TIREDOWNTHEROAD. MOSTOFITCOMESFROMTHEENERGYLOSTWHENTHE

TIREISDEFORMEDUNDERTHETRUCKASITMOVES.

7/29/2019 Rolling Resistance Explained

2/22 Fuel FAQs/1st Quarter 2012 2012, Bridgestone Americas Tire Operations, LLC. All rights reserved.

There are some practical things that can reduce

deformation and heat. Inflation pressure has an effect.

Underinflated tires deform much more, get much hotter,

and cut fuel economy. So properly inflated tires save fuel

by reducing rolling resistance.

What role can the tire itself play?

Tread design, casing design and rubber compoundingcan all reduce rolling resistance.

RIB TREADS tend to deform less as they roll than

do block or lug designs. If you dont need aggressive

tread patterns, a switch to rib-style treads can cut fuel

consumption.

DEEP TREADS tend to deform more and generate

more heat than shallow treads. So a rib-type shallow tread

tire, like a trailer tire, often has lower rolling resistance than

a deep drive design.

Likewise, worn tires usually have lower rolling

resistance than new tires of the same tread pattern.

CASING DESIGN can have significant effects on

rolling resistance. Since the casing must deform as a tire

rolls, anything that reduces that deformation, or the heat

associated with it, will save fuel. Radial tires were a giant

leap forward over bias tires in this respect. Casing design

and shape can often be optimized to reduce heat generation

and fuel consumption.

RUBBER COMPOUNDS can reduce heat loss and

rolling resistance too. Modern engineered synthetic rubber

and natural rubber blends can work together to minimize

rolling resistance in both tread and sidewalls.

TIRE TYPES can cut rolling resistance. Some wide

base single radial tires can carry the same loads as dual

pairs, but because theres just one tire, have half as many

sidewalls flexing as with a dual pair. That can reduce the

rolling resistance of the wheel end.

Nevertheless, dual tires specifically designed for low

rolling resistance may provide the same rolling resistance

as wide base tires. With duals, you do not have to change

wheels or maintenance practices to get best-in-class fue

economy.

Each of these factors can work individually, or together

For example, because aerodynamic resistance increases

much more rapidly with higher speeds than does tire rolling

resistance, a fuel efficiency advantage resulting from low

rolling resistance tires might be canceled by losses resultingfrom aerodynamic factors.

About our sources:

The information in this article was provided by Sales Engineering & Product Marketing, Bridgestone Commercial Solutions, Bridgestone AmericasTire Operations, LLC. To download a copy of this article, please visit:

www.bridgestonetrucktires.com

50 55 60 65 70 75 80

3.5

4

4.5

5

5.5

6

MPG

11.8% DIFFERENCE

AT 55 MPH

8.6% DIFFERENCE

AT 75 MPH

ADVANTAGE CUT 27%

4.21

3.88

5.30

4.86

5.47

6.12

SPEED (MPH)

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Effect of Speed on Tire

Fuel Efficiency

For more information on truck tires and fuel economy, visit us onlineat BridgestoneTruckTires.com.