This portion of the User’s Manual contains
tire safety information as required by 49 CFR 575.6.
Section 2.1 contains
“Steps for Determining Correct Load Limit - Trailer”.
Section 2.2 contains
“Steps for Determining Correct Load Limit – Tow Vehicle”.
Section 2.3 contains a
Glossary of Tire Terminology, including “cold inflation
pressure”, “maximum inflation pressure”, “recommended inflation
pressure”, and other non-technical terms.
Section 2.4 contains information from the
NHTSA brochure entitled
“Tire Safety – Everything Rides On It”.
This brochure This brochure, as well as the
preceding subsections, describes the following items;
·
Tire labeling,
including a description and explanation of each marking on the
tires, and information about the DOT Tire Identification Number
(TIN).
·
Recommended tire
inflation pressure, including a description and explanation of:
A.
Cold inflation pressure.
B.
Vehicle Placard and location on the vehicle.
C.
Adverse safety consequences of under inflation (including
tire failure).
D.
Measuring and adjusting air pressure for proper
inflation.
·
Tire Care, including
maintenance and safety practices.
·
Vehicle load limits,
including a description and explanation of the following items:
A.
Locating and understanding the load limit information,
total load capacity, and cargo capacity.
B.
Calculating total and cargo capacities with varying
seating configurations including quantitative examples showing /
illustrating how the vehicles cargo and luggage capacity
decreases as combined number and size of occupants’ increases.
This item is also discussed in Section 3.
C.
Determining compatibility of tire and vehicle load
capabilities.
D.
Adverse safety consequences of overloading on handling
and stopping on tires.
Determining the load
limits of a trailer includes more than understanding the load
limits of the tires alone. On all trailers there is a Federal
certification/VIN label that is located on the forward half of
the left (road) side of the unit. This certification/VIN label
will indicate the trailer’s Gross Vehicle Weight Rating (GVWR).
This is the most weight the fully loaded trailer can weigh. It
will also provide the Gross Axle Weight Rating (GAWR). This is
the most a particular axle can weigh. If there are multiple
axles, the GAWR of each axle will be provided.
If your trailer has a GVWR of 10,000 pounds or less, there is a
vehicle placard located in the same location as the
certification label described above. This placard provides tire
and loading information. In addition, this placard will show a
statement regarding maximum cargo capacity. Cargo can be added
to the trailer, up to the maximum weight specified on the
placard. The combined weight of the cargo is provided as a
single number. In any case, remember: the total weight of a
fully loaded trailer can not exceed the stated GVWR.
For trailers with living quarters installed, the weight of water
and propane also need to be considered. The weight of fully
filled propane containers is considered part of the weight of
the trailer before it is loaded with cargo, and is not
considered part of the disposable cargo load. Water however, is
a disposable cargo weight and is treated as such. If there is a
fresh water storage tank of 100 gallons, this tank when filled
would weigh about 800 pounds. If more cargo is being
transported, water can be off-loaded to keep the total amount of
cargo added to the vehicle within the limits of the GVWR so as
not to overload the vehicle. Understanding this flexibility will
allow you, the owner, to make choices that fit your travel
needs.
When loading your cargo, be sure it is distributed evenly to
prevent overloading front to back and side to side. Heavy items
should be placed low and as close to the axle positions as
reasonable. Too many items on one side may overload a tire. The
best way to know the actual weight of the vehicle is to weigh it
at a public scale. Talk to your dealer to discuss the weighing
methods needed to capture the various weights related to the
trailer. This would include the weight empty or unloaded,
weights per axle, wheel, hitch or king-pin, and total weight.
Excessive loads and/or underinflation cause tire overloading
and, as a result, abnormal tire flexing occurs. This situation
can generate an excessive amount of heat within the tire.
Excessive heat may lead to tire failure. It is the air pressure
that enables a tire to support the load, so proper inflation is
critical. The proper air pressure may be found on the
certification/VIN label and/or on the Tire Placard. This value
should never exceed the maximum cold inflation pressure stamped
on the tire.
1.1.1. Trailers
10,000 Pounds GVWR or Less
Tire and Loading Information Placard – Figure 1-1
1.
Locate the statement, “The weight of cargo should never
exceed XXX kg or XXX lbs.,” on your vehicle’s placard. See
figure 1-1.
2.
This figure equals the available amount of cargo and
luggage load capacity.
3.
Determine the combined weight of luggage and cargo being
loaded on the vehicle. That weight may not safely exceed the
available cargo and luggage load capacity.
The trailer’s placard refers to the Tire
Information Placard attached adjacent to or near the trailer’s
VIN (Certification) label at the left front of the trailer.
1.1.2. Trailers Over 10,000 Pounds GVWR (Note: These
trailers are not required to have a tire information placard on
the vehicle)
1.
Determine the empty weight of your trailer by weighing
the trailer using a public scale or other means. This step does
not have to be repeated.
2.
Locate the GVWR (Gross Vehicle Weight Rating) of the
trailer on your trailer’s VIN (Certification) label.
3.
Subtract the empty weight of your trailer from the GVWR
stated on the VIN label. That weight is the maximum available
cargo capacity of the trailer and may not be safely exceeded.
1.
Locate the statement, “The combined weight of occupants
and cargo should never exceed XXX lbs.,” on your vehicle’s
placard.
2.
Determine the combined weight of the driver and
passengers who will be riding in your vehicle.
3.
Subtract the combined weight of the driver and passengers
from XXX kilograms or XXX pounds.
4.
The resulting figure equals the available amount of cargo
and luggage capacity. For example, if the “XXX” amount equals
1400 lbs. and there will be five 150 lb. passengers in your
vehicle, the amount of available cargo and luggage capacity is
650 lbs. (1400-750 (5 x 150) = 650 lbs.).
5.
Determine the combined weight of luggage and cargo being
loaded on the vehicle. That weight may not safely exceed the
available cargo and luggage capacity calculated in Step # 4.
6.
If your vehicle will be towing a trailer, load from your
trailer will be transferred to your vehicle. Consult the tow
vehicle’s manual to determine how this weight transfer reduces
the available cargo and luggage capacity of your vehicle.
Accessory weight
The combined weight (in excess of those
standard items which may be replaced) of automatic transmission,
power steering, power brakes, power windows, power seats, radio
and heater, to the extent that these items are available as
factory-installed equipment (whether installed or not).
Bead
The part of the tire that is made of steel
wires, wrapped or reinforced by ply cords and that is shaped to
fit the rim.
Bead separation
This is the breakdown of the bond between
components in the bead.
Bias ply tire
A pneumatic tire in which the ply cords
that extend to the beads are laid at alternate angles
substantially less than 90 degrees to the centerline of the
tread.
Carcass
The tire structure, except tread and
sidewall rubber which, when inflated, bears the load.
Chunking
The breaking away of pieces of the tread or
sidewall.
Cold inflation pressure
The pressure in the tire before you drive.
Cord
The strands forming the plies in the tire.
Cord separation
The parting of cords from adjacent rubber
compounds.
Cracking
Any parting within the tread, sidewall, or
inner liner of the tire extending to cord material.
CT
A pneumatic tire with an inverted flange
tire and rim system in which the rim is designed with rim
flanges pointed radially inward and the tire is designed to fit
on the underside of the rim in a manner that encloses the rim
flanges inside the air cavity of the tire.
Curb weight
The weight of a motor vehicle with standard
equipment including the maximum capacity of fuel, oil, and
coolant, and, if so equipped, air conditioning and additional
weight optional engine.
Extra load tire
A tire designed to operate at higher loads
and at higher inflation pressures than the corresponding
standard tire.
Groove
The space between two adjacent tread ribs.
Gross Axle Weight Rating
The maximum weight that any axle can
support, as published on the Certification / VIN label on the
front left side of the trailer. Actual weight determined by
weighing each axle on a public scale, with the trailer attached
to the towing vehicle.
Gross Vehicle Weight Rating
The maximum weight of the fully loaded
trailer, as published on the Certification / VIN label. Actual
weight determined by weighing trailer on a public scale, without
being attached to the towing vehicle.
Hitch Weight
The downward force exerted on the hitch
ball by the trailer coupler.
Innerliner
The layer(s) forming the inside surface of
a tubeless tire that contains the inflating medium within the
tire.
Innerliner separation
The parting of the innerliner from cord
material in the carcass.
Intended outboard sidewall
The sidewall that contains a white-wall,
bears white lettering or bears manufacturer, brand, and/or model
name molding that is higher or deeper than the same molding on
the other sidewall of the tire or the outward facing sidewall of
an asymmetrical tire that has a particular side that must always
face outward when mounted on a vehicle.
Light truck (LT) tire
A tire designated by its manufacturer as
primarily intended for use on lightweight trucks or multipurpose
passenger vehicles.
Load rating
The maximum load that a tire is rated to
carry for a given inflation pressure.
Maximum load rating
The load rating for a tire at the maximum
permissible inflation pressure for that tire.
Maximum permissible inflation pressure
The maximum cold inflation pressure to
which a tire may be inflated.
Maximum loaded vehicle weight
The sum of curb weight, accessory weight,
vehicle capacity weight, and production options weight.
Measuring rim
The rim on which a tire is fitted for
physical dimension requirements.
Pin Weight
The
downward force applied to the 5th wheel or gooseneck
ball, by the trailer kingpin or gooseneck coupler.
Non-pneumatic rim
A mechanical device which, when a
non-pneumatic tire assembly incorporates a wheel, supports the
tire, and attaches, either integrally or separably, to the wheel
center member and upon which the tire is attached.
Non-pneumatic spare tire assembly
A non-pneumatic tire assembly intended for
temporary use in place of one of the pneumatic tires and rims
that are fitted to a passenger car in compliance with the
requirements of this standard.
Non-pneumatic tire
A mechanical device which transmits, either
directly or through a wheel or wheel center member, the vertical
load and tractive forces from the roadway to the vehicle,
generates the tractive forces that provide the directional
control of the vehicle and does not rely on the containment of
any gas or fluid for providing those functions.
Non-pneumatic tire assembly
A non-pneumatic tire, alone or in
combination with a wheel or wheel center member, which can be
mounted on a vehicle.
Normal occupant weight
This means 68 kilograms (150 lbs.) times
the number of occupants specified in the second column of Table
I of 49 CFR 571.110.
Occupant distribution
The distribution of occupants in a vehicle
as specified in the third column of Table I of 49 CFR 571.110.
Open splice
Any parting at any junction of tread,
sidewall, or innerliner that extends to cord material.
Outer diameter
The overall diameter of an inflated new
tire.
Overall width
The linear distance between the exteriors
of the sidewalls of an inflated tire, including elevations due
to labeling, decorations, or protective bands or ribs.
Ply
A layer of rubber-coated parallel cords.
Ply separation
A parting of rubber compound between
adjacent plies.
Pneumatic tire
A mechanical device made of rubber,
chemicals, fabric and steel or other materials, that, when
mounted on an automotive wheel, provides the traction and
contains the gas or fluid that sustains the load.
Production options weight
The combined weight of those installed
regular production options weighing over 2.3 kilograms (5 lbs.)
in excess of those standard items which they replace, not
previously considered in curb weight or accessory weight,
including heavy duty brakes, ride levelers, roof rack, heavy
duty battery, and special trim.
Radial ply tire
A pneumatic tire in which the ply cords
that extend to the beads are laid at substantially 90 degrees to
the centerline of the tread.
Recommended inflation pressure
This is the inflation pressure provided by
the vehicle manufacturer on the Tire Information label and on
the Certification / VIN tag.
Reinforced tire
A tire designed to operate at higher loads
and at higher inflation pressures than the corresponding
standard tire.
Rim
A metal support for a tire or a tire and
tube assembly upon which the tire beads are seated.
Rim diameter
This means the nominal diameter of the bead
seat.
Rim size designation
This means the rim diameter and width.
Rim type designation
This means the industry of manufacturer’s
designation for a rim by style or code.
Rim width
This means the nominal distance between rim
flanges.
Section width
The linear distance between the exteriors
of the sidewalls of an inflated tire, excluding elevations due
to labeling, decoration, or protective bands.
Sidewall
That portion of a tire between the tread
and bead.
Sidewall separation
The parting of the rubber compound from the
cord material in the sidewall.
Special Trailer (ST) tire
The "ST" is an indication the tire is for trailer use
only.
Test rim
The rim on which a tire is fitted for
testing, and may be any rim listed as appropriate for use with
that tire.
Tread
That portion of a tire that comes into
contact with the road.
Tread rib
A tread section running circumferentially
around a tire.
Tread separation
Pulling away of the tread from the tire
carcass.
Treadwear indicators (TWI)
The projections within the principal
grooves designed to give a visual indication of the degrees of
wear of the tread.
Vehicle capacity weight
The rated cargo and luggage load plus 68
kilograms (150 lbs.) times the vehicle’s designated seating
capacity.
Vehicle maximum load on the tire
The load on an individual tire that is
determined by distributing to each axle its share of the maximum
loaded vehicle weight and dividing by two.
Vehicle normal load on the tire
The load on an individual tire that is
determined by distributing to each axle its share of the curb
weight, accessory weight, and normal occupant weight
(distributed in accordance with Table I of CRF 49 571.110) and
dividing by 2.
Weather side
The surface area of the rim not covered by
the inflated tire.
Wheel center member
In the case of a non-pneumatic tire
assembly incorporating a wheel, a mechanical device which
attaches, either integrally or separably, to the non-pneumatic
rim and provides the connection between the non-pneumatic rim
and the vehicle; or, in the case of a non-pneumatic tire
assembly not incorporating a wheel, a mechanical device which
attaches, either integrally or separably, to the non-pneumatic
tire and provides the connection between tire and the vehicle.
Wheel-holding fixture
The fixture used to hold the wheel and tire
assembly securely during testing.
The National Traffic Safety Administration
(NHTSA) has published a brochure (DOT HS 809 361) that discusses
all aspects of Tire Safety, as required by CFR 575.6. This
brochure is reproduced in part below. It can be obtained and
downloaded from NHTSA, free of charge, from the following web
site:
http://www.nhtsa.dot.gov/cars/rules/TireSafety/ridesonit/tires_index.html
Studies of tire safety show that
maintaining proper tire pressure, observing tire and vehicle
load limits (not carrying more weight in your vehicle than your
tires or vehicle can safely handle), avoiding road hazards, and
inspecting tires for cuts, slashes, and other irregularities are
the most important things you can do to avoid tire failure, such
as tread separation or blowout and flat tires. These actions,
along with other care and maintenance activities, can also:
·
Improve vehicle
handling
·
Help protect you and
others from avoidable breakdowns and accidents
·
Improve fuel economy
·
Increase the life of
your tires.
This booklet presents a comprehensive
overview of tire safety, including information on the following
topics:
·
Basic tire
maintenance
·
Uniform Tire Quality
Grading System
·
Fundamental
characteristics of tires
·
Tire safety tips.
Use this information to make tire safety a
regular part of your vehicle maintenance routine. Recognize that
the time you spend is minimal compared with the inconvenience
and safety consequences of a flat tire or other tire failure.
Properly maintained tires improve the
steering, stopping, traction, and load-carrying capability of
your vehicle. Underinflated tires and overloaded vehicles are a
major cause of tire failure. Therefore, as mentioned above, to
avoid flat tires and other types of tire failure, you should
maintain proper tire pressure, observe tire and vehicle load
limits, avoid road hazards, and regularly inspect your tires.
Tire information placards and vehicle
certification labels contain information on tires and load
limits. These labels indicate the vehicle manufacturer's
information including:
·
Recommended tire
size
·
Recommended tire
inflation pressure
·
Vehicle capacity
weight (VCW–the maximum occupant and cargo weight a vehicle is
designed to carry)
·
Front and rear gross
axle weight ratings (GAWR– the maximum weight the axle systems
are designed to carry).
Both placards and certification labels are
permanently attached to the trailer near the left front.
Tire inflation pressure is the level of air
in the tire that provides it with load-carrying capacity and
affects the overall performance of the vehicle. The tire
inflation pressure is a number that indicates the amount of air
pressure– measured in pounds per square inch (psi)–a tire
requires to be properly inflated. (You will also find this
number on the vehicle information placard expressed in
kilopascals (kpa), which is the metric measure used
internationally.)
Manufacturers of passenger vehicles and
light trucks determine this number based on the vehicle's design
load limit, that is, the greatest amount of weight a vehicle can
safely carry and the vehicle's tire size. The proper tire
pressure for your vehicle is referred to as the "recommended
cold inflation pressure." (As you will read below, it is
difficult to obtain the recommended tire pressure if your tires
are not cold.)
Because tires are designed to be used on
more than one type of vehicle, tire manufacturers list the
"maximum permissible inflation pressure" on the tire sidewall.
This number is the greatest amount of air pressure that should
ever be put in the tire under normal driving conditions.
It is important to check your vehicle's
tire pressure at least once a month for the following reasons:
·
Most tires may
naturally lose air over time.
·
Tires can lose air
suddenly if you drive over a pothole or other object or if you
strike the curb when parking.
·
With radial tires,
it is usually not possible to determine underinflation by visual
inspection.
For convenience, purchase a tire pressure
gauge to keep in your vehicle. Gauges can be purchased at tire
dealerships, auto supply stores, and other retail outlets.
The recommended tire inflation pressure
that vehicle manufacturers provide reflects the proper psi when
a tire is cold. The term cold does not relate to the outside
temperature. Rather, a cold tire is one that has not been driven
on for at least three hours. When you drive, your tires get
warmer, causing the air pressure within them to increase.
Therefore, to get an accurate tire pressure reading, you must
measure tire pressure when the tires are cold or compensate for
the extra pressure in warm tires.
·
Step 1: Locate the
recommended tire pressure on the vehicle's tire information
placard, certification label, or in the owner's manual.
·
Step 2: Record the
tire pressure of all tires.
·
Step 3: If the tire
pressure is too high in any of the tires, slowly release air by
gently pressing on the tire valve stem with the edge of your
tire gauge until you get to the correct pressure.
·
Step 4: If the tire
pressure is too low, note the difference between the measured
tire pressure and the correct tire pressure. These "missing"
pounds of pressure are what you will need to add.
·
Step 5: At a service
station, add the missing pounds of air pressure to each tire
that is underinflated.
·
Step 6: Check all
the tires to make sure they have the same air pressure (except
in cases in which the front and rear tires are supposed to have
different amounts of pressure).
If you have been driving your vehicle and
think that a tire is underinflated, fill it to the recommended
cold inflation pressure indicated on your vehicle's tire
information placard or certification label. While your tire may
still be slightly underinflated due to the extra pounds of
pressure in the warm tire, it is safer to drive with air
pressure that is slightly lower than the vehicle manufacturer's
recommended cold inflation pressure than to drive with a
significantly underinflated tire. Since this is a temporary fix,
don't forget to recheck and adjust the tire's pressure when you
can obtain a cold reading.
To maintain tire safety, purchase new tires
that are the same size as the vehicle's original tires or
another size recommended by the manufacturer. Look at the tire
information placard, the owner's manual, or the sidewall of the
tire you are replacing to find this information. If you have any
doubt about the correct size to choose, consult with the tire
dealer.
The tire tread provides the gripping action
and traction that prevent your vehicle from slipping or sliding,
especially when the road is wet or icy. In general, tires are
not safe and should be replaced when the tread is worn down to
1/16 of an inch. Tires have built-in treadwear indicators that
let you know when it is time to replace your tires. These
indicators are raised sections spaced intermittently in the
bottom of the tread grooves. When they appear "even" with the
outside of the tread, it is time to replace your tires. Another
method for checking tread depth is to place a penny in the tread
with Lincoln's head upside down and facing you. If you can see
the top of Lincoln's head, you are ready for new tires.
To avoid vibration or shaking of the
vehicle when a tire rotates, the tire must be properly balanced.
This balance is achieved by positioning weights on the wheel to
counterbalance heavy spots on the wheel-and-tire assembly. A
wheel alignment adjusts the angles of the wheels so that they
are positioned correctly relative to the vehicle's frame. This
adjustment maximizes the life of your tires. These adjustments
require special equipment and should be performed by a qualified
technician.
The proper repair of a punctured tire
requires a plug for the hole and a patch for the area inside the
tire that surrounds the puncture hole. Punctures through the
tread can be repaired if they are not too large, but punctures
to the sidewall should not be repaired. Tires must be removed
from the rim to be properly inspected before being plugged and
patched.
1.5.9. Tire
Fundamentals
Federal law requires tire manufacturers to
place standardized information on the sidewall of all tires.
This information identifies and describes the fundamental
characteristics of the tire and also provides a tire
identification number for safety standard certification and in
case of a recall.
Please refer to the diagram below.
P
The "P" indicates the tire is for passenger vehicles.
Next number
This three-digit number gives the width in millimeters of
the tire from sidewall edge to sidewall edge. In general, the
larger the number, the wider the tire.
Next number
This two-digit number, known as the aspect ratio, gives
the tire's ratio of height to width. Numbers of 70 or lower
indicate a short sidewall for improved steering response and
better overall handling on dry pavement.
R
The "R" stands for radial. Radial ply construction of tires has
been the industry standard for the past 20 years.
Next number
This two-digit number is the wheel or rim diameter in
inches. If you change your wheel size, you will have to purchase
new tires to match the new wheel diameter.
Next number
This two- or three-digit number is the tire's load index.
It is a measurement of how much weight each tire can support.
You may find this information in your owner's manual. If not,
contact a local tire dealer. Note: You may not find this
information on all tires because it is not required by law.
M+S
The "M+S" or "M/S" indicates that the tire has some mud
and snow capability. Most radial tires have these markings;
hence, they have some mud and snow capability.
Speed Rating
The speed rating denotes the speed at which a tire is
designed to be driven for extended periods of time. The ratings
range from 99 miles per hour (mph) to 186 mph. These ratings are
listed below. Note: You may not find this information on all
tires because it is not required by law.
Please refer to the following diagram.
Tires for light trucks have other markings
besides those found on the sidewalls of passenger tires.
