
After loading the trailer, weigh
the trailer and then the tongue,
separately, to see if the weights are
proper. If they aren’t, adjustments
might be made by moving some
items around in the trailer.
Trailering may also be limited by
the vehicle’s ability to carry tongue
weight. Tongue weight cannot cause
the vehicle to exceed the GVWR
(Gross Vehicle Weight Rating) or the
RGAWR (Rear Gross Axle Weight
Rating). The effect of additional
weight may reduce the trailering
capacity more than the total of the
additional weight.
Consider the following example:
A vehicle model base weight is
5,500 lbs (2 495 kg); 2,800 lbs
(1 270 kg) at the front axle and
2,700 lbs (1 225 kg) at the rear axle.It has a GVWR of 7,200 lbs
(3 266 kg), a RGAWR of 4,000 lbs
(1 814 kg) and a GCWR (Gross
Combination Weight Rating) of
14,000 lbs (6 350 kg). The trailer
rating should be:
Expect tongue weight to be at least
10 percent of trailer weight (850 lbs
(386 kg)) and because the weight
is applied well behind the rear axle,
the effect on the rear axle is greater
than just the weight itself, as much
as 1.5 times as much. The weight
at the rear axle could be 850 lbs
(386 kg) X 1.5 = 1,275 lbs (578 kg).
Since the rear axle already weighs
2,700 lbs (1 225 kg), adding
1,275 lbs (578 kg) brings the total to
3,975 lbs (1 803 kg). This is veryclose to, but within the limit for
RGAWR as well. The vehicle is set to
trailer up to 8,500 lbs (3 856 kg).
If the vehicle has many options and
there is a front seat passenger and
two rear seat passengers with some
luggage and gear in the vehicle as
well. 300 lbs (136 kg) could be
added to the front axle weight and
400 lbs (181 kg) to the rear axle
weight. The vehicle now weighs:
Weight is still below 7,200 lbs
(3 266 kg) and you might think
700 additional pounds (318 kg)
should be subtracted from the
trailering capacity to stay within
GCWR limits. The maximum trailer
would only be 7,800 lbs (3 538 kg).
4-28 Driving Your Vehicle

Tire Size
The following illustration shows
an example of a typical
passenger vehicle tire size.
(A) Passenger (P-Metric) Tire
:The United States version of a
metric tire sizing system. The
letter P as the rst character in
the tire size means a passenger
vehicle tire engineered to
standards set by the U.S. Tire
and Rim Association.
(B) Tire Width
:The three-digit
number indicates the tire section
width in millimeters from sidewall
to sidewall.(C) Aspect Ratio
:A two-digit
number that indicates the tire
height-to-width measurements.
For example, if the tire size
aspect ratio is 60, as shown in
item C of the illustration, it would
mean that the tire’s sidewall is
60 percent as high as it is wide.
(D) Construction Code
:A letter
code is used to indicate the type
of ply construction in the tire.
The letter R means radial ply
construction; the letter D means
diagonal or bias ply construction;
and the letter B means
belted-bias ply construction.
(E) Rim Diameter
:Diameter of
the wheel in inches.
(F) Service Description
:These
characters represent the load
index and speed rating of the tire.
The load index represents the
load carry capacity a tire is
certi ed to carry. The speed
rating is the maximum speed a
tire is certi ed to carry a load.
Tire Terminology and
De nitions
Air Pressure:The amount of air
inside the tire pressing outward
on each square inch of the tire.
Air pressure is expressed in
pounds per square inch (psi)
or kilopascal (kPa).
Accessory Weight
:This means
the combined weight of optional
accessories. Some examples
of optional accessories are,
automatic transmission, power
steering, power brakes, power
windows, power seats, and air
conditioning.
Aspect Ratio
:The relationship
of a tire’s height to its width.
Belt
:A rubber coated layer of
cords that is located between the
plies and the tread. Cords may
be made from steel or other
reinforcing materials.
Service and Appearance Care 5-39

Bead:The tire bead contains
steel wires wrapped by steel
cords that hold the tire onto
the rim.
Bias Ply Tire
:A pneumatic
tire in which the plies are laid
at alternate angles less than
90 degrees to the centerline of
the tread.
Cold Tire Pressure
:The
amount of air pressure in a tire,
measured in pounds per square
inch (psi) or kilopascals (kPa)
before a tire has built up heat
from driving. SeeInflation - Tire
Pressure on page 5-42.
Curb Weight
:The weight of a
motor vehicle with standard
and optional equipment including
the maximum capacity of fuel,
oil, and coolant, but without
passengers and cargo.DOT Markings
:A code
molded into the sidewall of a
tire signifying that the tire is in
compliance with the U.S.
Department of Transportation
(DOT) motor vehicle safety
standards. The DOT code
includes the Tire Identi cation
Number (TIN), an alphanumeric
designator which can also
identify the tire manufacturer,
production plant, brand, and date
of production.
GVWR
:Gross Vehicle Weight
Rating. SeeLoading the Vehicle
on page 4-16.
GAWR FRT
:Gross Axle Weight
Rating for the front axle. See
Loading the Vehicle on
page 4-16.
GAWR RR
:Gross Axle Weight
Rating for the rear axle. See
Loading the Vehicle on
page 4-16.Intended Outboard Sidewall
:The side of an asymmetrical tire,
that must always face outward
when mounted on a vehicle.
Kilopascal (kPa)
:The metric
unit for air pressure.
Light Truck (LT-Metric) Tire
:A tire used on light duty trucks
and some multipurpose
passenger vehicles.
Load Index
:An assigned
number ranging from 1 to 279
that corresponds to the load
carrying capacity of a tire.
Maximum In ation Pressure
:The maximum air pressure to
which a cold tire can be in ated.
The maximum air pressure is
molded onto the sidewall.
Maximum Load Rating
:The load rating for a tire at the
maximum permissible in ation
pressure for that tire.
5-40 Service and Appearance Care

Maximum Loaded Vehicle
Weight:The sum of curb
weight, accessory weight,
vehicle capacity weight, and
production options weight.
Normal Occupant Weight
:The
number of occupants a vehicle
is designed to seat multiplied by
150 lbs (68 kg). SeeLoading
the Vehicle on page 4-16.
Occupant Distribution
:Designated seating positions.
Outward Facing Sidewall
:The
side of an asymmetrical tire that
has a particular side that faces
outward when mounted on a
vehicle. The side of the tire that
contains a whitewall, bears white
lettering, or bears manufacturer,
brand, and/or model name
molding that is higher or deeper
than the same moldings on the
other sidewall of the tire.Passenger (P-Metric) Tire
:A tire used on passenger cars
and some light duty trucks and
multipurpose vehicles.
Recommended In ation
Pressure
:Vehicle
manufacturer’s recommended
tire in ation pressure as
shown on the tire placard. See
Inflation - Tire Pressure on
page 5-42andLoading the
Vehicle on page 4-16.
Radial Ply Tire
:A pneumatic
tire in which the ply cords that
extend to the beads are laid at
90 degrees to the centerline of
the tread.
Rim
:A metal support for a tire
and upon which the tire beads
are seated.
Sidewall
:The portion of a tire
between the tread and the bead.
Speed Rating
:An alphanumeric
code assigned to a tire indicating
the maximum speed at which a
tire can operate.Traction
:The friction between
the tire and the road surface.
The amount of grip provided.
Tread
:The portion of a tire that
comes into contact with the road.
Treadwear Indicators
:Narrow
bands, sometimes called wear
bars, that show across the tread
of a tire when only 1/16 inch
(1.6 mm) of tread remains. See
When It Is Time for New Tires on
page 5-50.
UTQGS (Uniform Tire Quality
Grading Standards)
:A tire
information system that provides
consumers with ratings for a tire’s
traction, temperature, and
treadwear. Ratings are
determined by tire manufacturers
using government testing
procedures. The ratings are
molded into the sidewall of the
tire. SeeUniform Tire Quality
Grading on page 5-52.
Service and Appearance Care 5-41

Vehicle Capacity Weight:The
number of designated seating
positions multiplied by 150 lbs
(68 kg) plus the rated cargo load.
SeeLoading the Vehicle on
page 4-16.
Vehicle Maximum Load on the
Tire
:Load on an individual tire
due to curb weight, accessory
weight, occupant weight, and
cargo weight.
Vehicle Placard
:A label
permanently attached to a
vehicle showing the vehicle’s
capacity weight and the
original equipment tire size
and recommended in ation
pressure. See “Tire and Loading
Information Label” underLoading
the Vehicle on page 4-16.
In ation - Tire Pressure
Tires need the correct amount of
air pressure to operate
effectively.
Notice:Do not let anyone tell
you that under-in ation or
over-in ation is all right. It is
not. If your tires do not have
enough air (under-in ation),
you can get the following:
Too much exing
Too much heat
Tire overloading
Premature or irregular wear
Poor handling
Reduced fuel economy
If your tires have too much air
(over-in ation), you can get
the following:
Unusual wear
Poor handling
Rough ride
Needless damage from road
hazardsA vehicle speci c Tire and
Loading Information label is
attached to your vehicle. This
label shows your vehicle’s
original equipment tires and the
correct in ation pressures for
your tires when they are cold.
The recommended cold tire
in ation pressure, shown on the
label, is the minimum amount of
air pressure needed to support
your vehicle’s maximum load
carrying capacity.
For additional information
regarding how much weight
your vehicle can carry, and an
example of the Tire and Loading
Information label, seeLoading
the Vehicle on page 4-16. How
you load your vehicle affects
vehicle handling and ride
comfort. Never load your vehicle
with more weight than it was
designed to carry.
5-42 Service and Appearance Care