Rolling Resistance Explained
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Transcript of Rolling Resistance Explained
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7/29/2019 Rolling Resistance Explained
1/2
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.
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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)
/PO'VFM&GmDJFOU5JSF'VFM&GmDJFOU5JSF
Effect of Speed on Tire
Fuel Efficiency
For more information on truck tires and fuel economy, visit us onlineat BridgestoneTruckTires.com.