Two New Tires Should be Mounted on the Rear

Abstract

When the rear wheels of a vehicle lose grip on the road, a driver's ability to control the vehicle is dramatically reduced, a phenomenon called oversteer. Oversteer is an event that occurs in many rollovers and single vehicle loss-of-control accidents. Therefore, when replacing two tires, the two new tires (the tires with better tread) should always be mounted on the rear wheels. There are virtually no exceptions to this rule and it is clearly demonstrated in tests conducted by one major tire manufacturer (Michelin, 2008). The present studies examined whether people are aware of this rule by asking them where two new replacement tires should be installed on a vehicle. Results showed that approximately 75% of consumers did not know to install two new replacement tires in the two rear wheel positions. Warning systems are discussed with focus on making recommendations for improving safety communications to tire installer and consumers.

Full text

Two New Tires Should be Mounted on the Rear
Jeffrey J. Smith, Jennifer A. Cowley, and Michael S. Wogalter
Psychology Department, North Carolina State University
Raleigh, NC 27695-7650 USA
When the rear wheels of a vehicle lose grip on the road, a driver's ability to control the vehicle is
dramatically reduced, a phenomenon called oversteer. Oversteer is an event that occurs in many
rollovers and single vehicle loss-of-control accidents. Therefore, when replacing two tires, the
two new tires (the tires with better tread) should always be mounted on the rear wheels. There
are virtually no exceptions to this rule and it is clearly demonstrated in tests conducted by one
major tire manufacturer (Michelin, 2008). The present studies examined whether people are
aware of this rule by asking them where two new replacement tires should be installed on a
vehicle. Results showed that approximately 75% of consumers did not know to install two new
replacement tires in the two rear wheel positions. Warning systems are discussed with focus on
making recommendations for improving safety communications to tire installer and consumers.
INTRODUCTION
Warnings are a form of safety communication intended
to inform persons about risks and hazards and to
minimize undesirable consequences, such as illness,
injury, or property damage (e.g., Wogalter & Dingus,
1999; Wogalter & Laughery, 2006). Warnings are the
third stage of the well-known hierarchy of hazard
control: (1) design out the hazard, (2) guard against the
hazard, and (3) provide adequate warnings for both
proper use and reasonably foreseeable misuses (Sanders
& McCormick, 1993). When hazards cannot be
designed out or guarded against, manufacturers should
use an effective warning system, which may involve
information on the product itself, in the product manual,
and other methods of communication (see, e.g.,
Wogalter & Laughery, 2006).
Manufacturers have a general – and often legal –
responsibility to alert consumers and downstream
entities of safety-related information or warnings (see,
e.g., Cox & Wogalter, 2006). The communication-
human information processing model describes how
information is passed from the source to the receiver and
allows responsible entities to identify where bottlenecks
can occur in the communication process (see, e.g.,
Wogalter, DeJoy, & Laughery; 1999; Wogalter, 2006).
It also helps to identify why certain communications do
not produce appropriate precautionary behaviors. A
communication flow between source and receiver that
produces appropriate behaviors becomes important when
hazards are not easily perceived or obvious.
In the modern era, technologies have brought
with it hazards that are not necessarily obvious to
consumers. Some of the newest (and often overlooked)
automotive technological advances pertain to vehicle
tires. Although tires have become increasingly more
reliable, when tire failure occurs it can result in
catastrophic injury or death. Previous research shows
that many people do not know many aspects of
automotive maintenance, including those involving tires
(Cowley, Kim & Wogalter, 2006; Kalsher, Wogalter,
Lim, & Laughery, 2005; Mayer & Laux, 1990).
One potentially important fact about tires has
been recently revealed in litigation and in systematic
testing: when replacing two tires (rather than four) on a
vehicle, the new tires should typically be placed on the
two rear wheel positions to reduce the likelihood of
oversteer which is sometimes also called fishtailing
(Michelin’s website, 2008). Oversteer is a phenomenon
that occurs when the rear wheels of a vehicle lose grip
with the road, which can drastically reduce the driver’s
ability to control their vehicle.
Oversteer has been identified as a causal factor
in many vehicle rollovers and single vehicle loss-of-
control accidents. The phenomenon is particularly
pronounced in hydroplaning situations where water
between the tire and the road surface reduces or
eliminates the friction involved in tire traction. If the
front wheels lose traction first, the driver is more likely
to notice the event and make compensatory maneuvers
to reduce likelihood of complete loss of control; this
contrasts with the loss of traction in the rear, which
makes compensatory maneuvers more difficult, if not
impossible, to execute. That is, when the rear wheels
lose traction first, there is complete loss of control that
even experienced, professional test track drivers have
difficulty maneuvering out of safely. Given these
circumstances, when replacing just two tires, the new
tires with the best tread should always be mounted in the
rear because tires with more tread can potentially
PROCEEDINGS of the HUMAN FACTORS AND ERGONOMICS SOCIETY 52nd ANNUAL MEETING—2008 1743
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displace more water than the same tires with less tread,
resulting in more traction with the road surface. There
are virtually no exceptions to this rule (e.g., tires are
different sizes in the front and rear). The phenomenon
of oversteer in a hydroplaning situation from reduced
tread on the rear versus the front is demonstrated in tests
conducted by one major tire manufacturer, Michelin, and
shown on its website (Michelin, 2008).
Given its relevance to safety, it would seem
important that people know about the 2-tire placement
rule. However, information about it does not appear to
be widely available, other than its mention in some
manufacturer's technical materials and on the website
mentioned above. For example, the authors have not
been able to locate information on the 2-tire placement
rule in any vehicle owner's manual. Given the apparent
sparseness of available information, it would seem that
information on the 2-tire placement rule has not been
adequately disseminated. The present study examines
people's knowledge about where two new tires should be
installed on a vehicle.
METHOD
Participants
Two samples were collected approximately 5 months
apart, involving participants from North Carolina State
University and the surrounding community (total N =
230). Each participant completed a consent form, a
demographics form and a large multi-sectioned
questionnaire. The data described in this report are
taken from a subsection of this questionnaire involving
automotive safety.
The first group comprised 137 participants.
Forty-two were non-student adults (mean age = 41.1
years, SD = 17.0) of which 23 were males and 19 were
females). Ninety-five were undergraduate students from
the North Carolina State University (mean age = 20.2
years, SD 1.95) of which 51 were males and 86 were
females).
The second group comprised 93 participants.
Forty seven non-student adults (mean age = 37.9 years,
SD = 14.5) of which 25 were males and 22 were
females. Forty six were undergraduate from the North
Carolina State University (mean age = 21.7 years, SD
=3.35) with 30 males and 15 females.
Questionnaire
All participants were presented the following
information:
Suppose you were replacing only two worn tires
rather than all four. Where would you mount
the TWO new tires? Please put a check mark
next to the TWO places you would mount or
request to mount 2 new tires (with the best tread)
on a vehicle. Please check only two blanks. For
this question ignore any involvement of a spare tire.
Front of Vehicle
__ __
Left Front Tire Right Front Tire
__ __
Left Rear
Tire Right Rear Tire
Rear of Vehicle
Since there were some comments by the first group of
participants that placement of the tires depended on the
vehicle's drive train, an additional question was asked of
the second group of participants. It should be noted,
however, that the 2-tire rule is not affected by the kind
drive train. The question was asked to determine in a
more systematic way if this was a belief by participants.
The specific question was:
Did you answer the above question based upon
the vehicle’s drive train (whether the vehicle
was front-wheel drive, rear-wheel drive, four-
wheel drive, etc.)?
If “yes”, indicate which of the following you
considered when marking your decision
about the placement of two new tires.
_____ For a front-wheel drive vehicle
_____ For a rear-wheel drive vehicle
_____ For an all- (or 4-) wheel drive vehicle
_____
It does not matter what drive train it is
_____ I don’t know
RESULTS
For the first group of participants, the data showed that
only 31 of 131 (23.7%) participants correctly indicated
that one of the tires should be placed on the right rear
wheel and one on the left rear wheel.
For the second group of participants, only 23 of
93 (24.7%) participants correctly indicated that two tires
should be placed on the two rear wheel positions.
PROCEEDINGS of the HUMAN FACTORS AND ERGONOMICS SOCIETY 52nd ANNUAL MEETING—2008 1744

Thus, out of all 230 participants in both groups,
only 54 properly indicated that both tires would be
placed in the rear; 146 participants indicated that both
tires should be placed in the front. Thirty indicated
various other combinations of placements.
The second group of participants was asked
whether the placement of the two new tires depended on
the drive train. Fifty-four of 93 (58.0%) of participants
incorrectly believed that the vehicle’s drive train
influences the decision about where to place the 2 new
replacement tires.
DISCUSSION
The present study concerned people's knowledge about
the correct placement of two new tires on vehicles. The
issue is important because incorrect placement could
affect vehicle handling and the ability to control the
vehicle in certain situations, such as hydroplaning. The
results showed that most people believed the correct
placement of two new tires was on the front wheels.
This is incorrect. A much smaller percentage of
individuals correctly stated that two new tires should be
placed on the rear wheels. Thus, the location that most
participants chose to place two new tires would increase
the likelihood of oversteer or fishtailing, particularly
during hydroplaning situations, compared to proper tire
placement (Michelin, 2008).
In addition some participants indicated that the
correct tire placement depends on drive train (e.g., front
wheel, rear-wheel, etc.). However, the 2-tire placement
principle does not, in fact, depend on the drive train.
Rather the 2-tire placement rule almost always holds,
virtually without exception (e.g., differences in tire sizes
in the front and rear).
The finding of the large amount of incorrect
responses has several implications with regard to safety.
One is that people have not been provided adequate
information about the 2-new tire placement rule by tire
and vehicle manufacturers, writers of automotive writers
in popular venues, and insurers. It is not clear why this
is the case, but there is some precedent in the lack of
communication of tire safety and maintenance. For
example, several recent studies have demonstrated that
many people do not know very much regarding tire
aging (Cowley et al., 2006; Kalsher et al., 2005). Thus,
entities that have (or should have) knowledge about tire-
related hazards have not yet employed an adequate
communication campaign regarding hazards associated
with tire use, except perhaps with regard to tire pressure
and amount of tread. Communication of these and other
relevant facts are important to prevent tire failure and the
potential consequences of serious injury or death.
While several entities could have be involved in
communicating the 2-new tire placement rule, it is the
manufacturer that has (or should have) superior
knowledge about their product's characteristics and
which have most responsibility to communicate the
hazards. The manufacturer should strive to ensure that
relevant entities receive appropriate warning
information. This includes information communicated
to purchasers directly through labels and product
manuals and indirectly via the middle entities
communicating the information to the receivers down
the line.
Effective warnings related to tire replacement
safety could also be distributed from the manufacturer
through some or all of the following example channels:
• On the tires themselves
• Video, audio, pictorial, and text warnings on
manufacturer’s websites (e.g., Michelin, 2008)
• Posters and printable flyers to be placed in
customer waiting rooms, behind service desks,
etc., at tire seller and installer locations
• Safety bulletins distributed to tire seller and
installer for multi-channel distribution (i.e.,
brick-and-mortar establishments as well as
websites)
• Emails as warnings and reminders to end users
who have purchased products, as well as sellers
and installers
• Training information that could be incorporated
into tire seller and installer training and
orientation programs
• Safety articles for car enthusiast and related
magazines and websites
The proliferation of the Internet and online
media distribution would enable manufacturers to more
widely distribute warning information to installers, end
users, as well as other entities at relatively low cost.
However, until the Internet access is truly ubiquitous, it
cannot be assumed that this method is a primary way for
people to acquire information. Nonetheless, it is a
growing method that should increasingly be developed
with regard to providing relevant safety information.
On-product labeling and other accompanying
information at the time of product purchase are still the
primary ways of communicating product hazards.
Additionally, entities installing tires should be provided
some ways of giving persuasive information to tire
purchasers so as to aid in proper decision-making about
where to place two new tires on vehicles.
Additional research could involve (a) collection
of data from tire sellers and installers regarding their
awareness of the 2-tire placement rule, (b) asking actual
purchasers of replacement tires where they plan on
having them mounted, and (c) continued evaluation of
the aforementioned information distribution channels
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and methods to ascertain effectiveness for various
information campaigns concerning the 2-tire placement
rule.
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