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Recreational Vehicle Tire Care and Safety Guide
Here are guidelines
to help you obtain the best performance from the tires used on your recreational
vehicle (RV). Unless otherwise specified, the term "RV" applies to
motor homes, travel trailers, 5th-wheel travel trailers and slide-in campers
for pickup trucks. More information about your specific vehicle and its tires
is contained in the owner's manual supplied by the vehicle manufacturer. Additional
information concerning your tires is available from your local tire dealer or
the tire manufacturer.
Tires used on RVs
are subjected to a greater variety of conditions than automobile applications.
Many RVs are out of service for long periods of time. When RVs are being driven,
they are used at or near maximum loads during hot weather.
Normal, natural aging
of a tire, as well as ozone in the air, may cause the rubber to crack, especially
in the sidewall area. Tires should be checked for this condition or other damage
before every long trip. Tires over five years old or ones that show signs of
cracking should be inspected regularly by a tire professional to determine if
they should remain in service or be discarded.
Certification
Label
Proper
RV Tire Inflation
Vehicle
Weighing Procedures
Dangers
of Vehicle Overloading
Tire
Maintenance
CERTIFICATION
LABEL
Recreational vehicles
manufactured since 1972 have a certification label which provides the following
information relating to tires and loads:
1. Gross Vehicle
Weight Rating (GVWR)
2. Gross Axle Weight
Ratings (GAWR) for each axle
3. Tire and rim
sizes
4. Recommended cold
tire inflation pressures
Example of a certification label
The certification
label can be found on several different locations within your vehicle, including
(but not limited to) the driver's hinge pillar, door latch post, etc. Vehicles
manufactured before 1972 may not have a certification label, and the tire and
loading information will only be found in the owner's manual.
Your manual also
contains information about alternate tire sizes. Be sure to follow all recommendations
in your owner's manual regarding the use of these alternative tire sizes. If
you are considering changing to a tire size other than those shown on the certification
label, be sure to consult with your vehicle manufacturer, tire dealer or tire
manufacturer. Using the wrong size tire can lead to tire failure.
Vehicle modifications
such as lift kits and other suspension alterations and/or use of tires not recommended
by the vehicle or tire manufacturer can adversely affect vehicle handling and
stability. Tires specifically designed for travel trailer use in highway
service have an "ST" molded on the tire sidewall, such as ST225/75R15.
The "ST" stands for "Special Trailer" and means the tire
is designed specifically for trailer service.
PROPER
RV TIRE INFLATION
The most important
factors in tire care are maintaining proper inflation pressures, avoiding excess
loading, inspecting tires regularly and driving with care at appropriate speeds.
It is important
that your tires be properly inflated. Failure to maintain correct inflation
pressures may result in fast and uneven treadwear, improper vehicle handling,
and excessive heat buildup, which may result in tire failure.
To make sure you
maintain the correct pressure in your tires, check the air pressure regularly
with your own dual-head inflation gauge that is calibrated up to 120 psi at
2 psi increments. The recommended inflation pressures for your tires are indicated
on the certification label or in your owner's manual. However, since RVs can
be configured and loaded in many different ways, the proper inflation pressure
should be determined by actual tire loads. The actual loads can be determined
by physically weighing the vehicle. These loads will change from trip to trip,
depending on how the vehicle is loaded.
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WARNING
Serious Injury May Result From:
Tire Failure
Due to Underinflation/Overloading
Follow owner's manual or certification label in vehicle.
Explosion
of tire/rim assembly due to improper mounting
Only specially trained persons should mount tires.
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Check your
tires' air pressures at least once a month, before each trip, and each
morning you drive during a trip. Inflation pressures should be checked
when tires are "cold," that is, before they have been driven
one mile. Heat generated during driving increases air pressure above the
proper cold inflation pressure. This is normal, so never "bleed"
air from a hot tire, since this could result in dangerous underinflation.
It may be difficult
to check the air pressures of inside tires in dual fitments. (A dual fitment
is two tires on the same side of an axle.) However, it is important that
these air pressures be maintained because the inside dual tires are subjected
to high heat exposure (from brakes), lower air circulation and crowned
road surfaces (which can cause inside dual tires to support more of the
load than the outside dual tires).
Make sure all
tire valves and extensions are equipped with valve caps to keep out dirt
and moisture. Installing a new valve assembly is good practice whenever
a tire is replaced.
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VEHICLE WEIGHING PROCEDURES
You can ensure the
tires on your RV or travel trailer are not overloaded by maintaining the proper
inflation pressure and by never exceeding your vehicle's Gross Axle Weight Ratings
(GAWR) or the Gross Vehicle Weight Rating (GVWR). (Remember: this information
can be found on the certification label or in your vehicle owner's manual.)
The vehicle load must be distributed so that no individual axle, tire or dual
assembly is overloaded.
How to Determine
Your RV’s Actual Weight
The major components
of an RV -- the vehicle frame, brakes, axles, rims, tires, etc. -- are designed
to accommodate a particular weight. If these weight ratings are exceeded, these
parts may wear rapidly. The RV manufacturer provides the weight ratings and
load specifications printed on the vehicle certification label. There are five
weight-related terms you should know:
1. GVWR: Gross
Vehicle Weight Rating
GVWR is the weight rating established by the chassis manufacturer as the maximum
weight (including vehicle, cargo, liquids, passengers, etc.) that the components
of the chassis are designed to support.
2. GAWR: Gross
Axle Weight Rating (for each axle)
This is the maximum
weight rating that components of each axle are designed to support (i.e.,
tires, wheels, brakes, springs, axle). This is determined by the lowest design
capacity of any component. In other words, if the wheels have the lowest design
capacity of any component on that axle, installing tires with a higher load
capacity does not increase the GAWR.
3. GCWR: Gross
Combined Weight Rating
GCWR represents the maximum allowable total loaded weight rating of the motor
vehicle and any trailer it is towing. GCWR minus GVWR represents the allowable
weight for the towed vehicle.
4. GVW: Gross
Vehicle Weight
GVW is the actual weight of a fully loaded vehicle (i.e., vehicle, cargo,
liquids/fuels, passengers, towed vehicles, tongue weight, etc.) The GVW must
not exceed the GVWR.
5. GAW: Gross
Axle Weight
GAW is the actual weight of a fully loaded vehicle carried by a single axle.
Due to the many ways that weight can be distributed within an RV, GAW can
often provide a false sense of security. Even though the weight of the total
axle may be within the axle's rating, it may be overloaded on one side.
Where to Weigh
Your RV/Travel Trailer
To weigh your RV
correctly, measure the fully loaded vehicle, axle by axle and wheel position
by wheel position. you can find several certified public or commercial scales
at moving and storage lots, farm suppliers with grain elevators, gravel pits,
recycling companies, and large commercial truck stops. (Also look in the telephone
book under "weighers" or "weighing.") Allow adequate time,
since the entire weighing process can take up to 30 minutes. There may be a
small fee for each weight taken, but the expense is a worthwhile investment
towards the safe and economical operation of your vehicle.
How to Weigh Your
RV
Your RV must be weighed
fully loaded, that is, with passengers, food, clothing, fuel, water, propane,
supplies, etc. Any towed vehicle (car/pickup, boat or trailer) or item loaded
on brackets on the back of the RV, such as bikes or motorcycles, should also
be included in the weighing.
There are three types
of scales:
1. PLATFORM
- This scale is long enough to weigh the complete vehicle. The following steps
are suggested:
a. Pull onto the
scale so that only the front axle is on the platform (with the end of the
scale midway between the front and rear axles), and record the scaled weight.
b. Pull forward
until the full unit is on the scale weight.
c. Pull forward
so that only the rear axle is on the scale (again with the edge of the scale
midway between the front and drive axles), and record the scaled weight.
d. If the RV has
a rear tag axle, pull forward so that only the tag axle remains on the scale,
and record the scaled weight.
If there is no
towed vehicle, this weight will represent the actual weight on the tag axle.
To determine the actual load on the drive axle, subtract this value from the
recorded weight in step 1c. If there is a towed vehicle, proceed to step 1e
to obtain the "towed vehicle only" weight. Subtract that value from
the value above and then subtract that from the weight recorded in step 1c.
e. If a boat, trailer
or other vehicle is being towed, it should be weighed and combined with the
towing vehicle's GVW to ensure the total weight does not exceed the GCWR.
2. SEGMENTED PLATFORM
- Platform scales with segmented sections can provide individual axle weights
and total vehicle weights simultaneously, when the vehicle is positioned properly.
Position the vehicle
on the scales so that each axle centered as much as possible on separate segments,
and record the weight. Reposition the vehicle so that only one side is on the
scale, again centered on the segment as much as possible. Subtract the weighed
wheel positions from the total axle weights to determine the unweighed wheel
positions' weights.
3. SINGLE AXLE
- This scale weighs one axle at a time. Drive your front axle onto the scale
and stop long enough for the weight to be recorded. Pull vehicle forward until
the rear axle is on the scale. To obtain the gross vehicle weight, add the two
axle loads together. To obtain the individual wheel position weights, repeat
this process with only one side of the RV on the scale.
Note: Even
though the weight of the total axle may be within the axle's rating, it may
be overloaded on one side. This causes one wheel position to be overloaded.
Therefore, side-to-side weighing should also be done.
To determine individual
wheel position weights, it is necessary to repeat the previous three steps
(1a, 1b, and 1c), but this time, use only one side of the scale.
To calculate the
opposite side of the vehicle wheel position weight, subtract this side's weights
from the weights recorded in steps 1a, 1b, and 1c.
Your RV must remain
as level as possible on the scale (even though an axle or side is not physically
on the scale). Obviously, to obtain the side-to-side weights, there must
be enough space on either side of the scale to accommodate the RV being partially
off the scale.
If there is a difference
in the weights on one side of the vehicle as compared to weights on the other
side, components (tires, wheels, brakes, springs, etc.) on the heavier side
could be overloaded, even though the total axle load is within the GAWR. It
is important to redistribute the load to avoid component failure, as well as
to improve the handling characteristics of the vehicle.
With these actual
weights, it is now possible to compare them against the GAWR, GVWR and tire
capacities. These weights are also what should be used to help determine the
proper air pressure for the tires.
How to Weigh Your
Travel Trailer
To properly weigh
a travel trailer, it should first be weighed, including the tongue weight, while
detached from the pulling vehicle. This actual overall weight must be less than
or equal to the GVWR for safe operation. If the overall weight is greater than
the GVWR, some contents must be removed until maximum GVWR limitations are achieved.
Once the actual overall weight is determined and the trailer is within GVWR
limits, the following weights must be determined:
1. Weight of complete
trailer, while attached, but excluding towed vehicle. This will result in
the actual weight which is exerted on all of the trailer tires. This weight
may be subtracted from the overall trailer weight (above) to determine actual
"tongue" weight.
2. With the trailer
still attached to the towed vehicle, each wheel position should then be weighed
separately to be sure each tire is not overloaded. If and overload condition
exists on any wheel position, trailer loading must be redistributed or removed.
If an overload situation is not corrected, tire or mechanical failures may
occur.
3. The individual
wheel positions (particularly the rear positions) on the towing vehicle should
also be weighed for possible overload while the trailer remains attached.
This is especially important on 5th-wheel applications where tongue weight
may be extreme.
DANGERS
OF VEHICLE OVERLOADING
The results of overloading
can have serious consequences in terms of passenger safety. Too much weight
for your vehicle's suspension system can cause spring, shock absorber or brake
failure, handling or steering problems, irregular tire wear, tire failure or
other damage. An overloaded vehicle is hard to drive and hard to stop. In cases
of serious overloading, brakes can fail completely, particularly on steep hills.
The load a tire will carry safely is a combination of the size of the tire,
its load range and corresponding inflation pressure. Overloading your RV, with
underinflated tires, can spell trouble.
Excessive loads and/or
underinflation cause "tire overloading." As a result, abnormal tire
flexing occurs, which can generate an excessive amount of heat within the tire.
Excessive heat may exceed the tire's capabilities, which may lead to tire failure.
It is the air pressure
which enables a tire to support the load, so proper inflation is critical. Since
RVs can be configured and loaded in many different ways, air pressures must
be determined from the actual loads (determined by weighing) and taken from
the load and inflation tables provided by the tire manufacturer. These air pressures
may differ from those found on the certification label. However, they should
never exceed the tire limitation for load or air pressure.
If you discover that
your tires cannot support the actual weights, lighten the load or install tires
with a higher carrying capacity.
Note: Installing
tires with a higher carrying capacity only solves the problem of tire overload.
It has no effect on the overloading of other components (i.e., rims, axles,
shocks, or bearings). Rims may not be capable of withstanding the higher pressures
necessary to support the load.
If the load cannot
be adequately reduced, contact the RV manufacturer for advice.
If you decide to
install a tire size other than that originally provided on the vehicle, care
must be taken to ensure adequate load-carrying capacity and compatibility between
the tire and rim.
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WARNING
There is a
danger of serious injury or death if a tire of one bead diameter is installed
on a rim or wheel of a different rim diameter. Always replace a
tire with another tire of exactly the same bead diameter designation and
suffix letters. For example: A 16" tire goes on a 16" rim. Never
mount a 16" tire on a 16.5" rim. A 16.5" tire goes on a 16.5" rim. Never
mount a 16.5" tire on a 16" rim.
While it is
possible to pass a 16" diameter tire over the lip of flanges of a 16.5"
size rim, it cannot be inflated enough to position itself against the
rim flange. If an attempt is made to seat the tire bead by inflating,
the tire bead will break with explosive force and could cause serious
injury or death.
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If you have operated
your vehicle with an underinflated tire, promptly have it removed from the wheel
for a complete internal inspection to be sure it is not damaged. Tires driven
even short distances while underinflated may be damaged beyond repair.
Tires should be inspected
regularly for excessive or irregular treadwear, bulges, aging, fabric breaks,
cuts or other damages. Remove any nails, stones, glass, etc., embedded in the
tread to prevent damage. Even minor damage can lead to tire failure. Replace
tires when the tread is worn to 2/32" depth remaining in two or more adjacent
grooves.
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Built-in treadwear
indicators, or "wear bars," which look like narrow strips of smooth rubber
across the tread, will appear on the tire when that point of wear is reached.
When you see these wear bars, the tire is worn out and it's time to replace
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On vehicles with
GVWR in excess of 10,000 pounds, federal regulations require that tires on the
front axle be removed when worn down to 4/32" depth. It may also be desirable
to replace tires prior to wearing down to 4/32" to improve traction or
vehicle handling.
Load and cold inflation
pressure imposed on a rim/wheel must not exceed the rim/wheel manufacturer's
recommendation, even though the tire may be marked for a higher load and inflation.
Matching radial tires
with rim/wheels must be done with extreme care. Not all older rims/wheels are
approved for use with radial tires. Consult the rim/wheel manufacturer or local
distributor or your tire dealer, to determine which rims/wheels are acceptable
for use with a specific radial tire.
If your tires show
uneven wear, ask a serviceperson to check for and correct any misalignment,
imbalance, or other mechanical problem involved.
Tires will wear out
faster when subjected to high speeds as well as hard cornering, rapid starts,
sudden stops and frequent driving on surfaces which are in poor condition. Surfaces
with holes and rocks or other objects can damage tires and cause wheel misalignment.
When you drive on such surfaces, drive on them carefully and slowly. Before
driving at normal or highway speeds, examine your tires for any damage, such
as cuts or penetrations.
Check your tires
frequently for scrapes, bulges, cuts, snags, or impact damage. Damage can occur
to the inner portions of your tire without being visible on the outside. While
driving, if you experience a sudden vibration or ride disturbance, or if you
suspect that damage to your tires or vehicle has occurred, immediately reduce
your speed or stop. Drive with caution or have your vehicle towed to the nearest
vehicle or tire dealer to have your vehicle inspected.
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WARNING
Tire changing
can be dangerous and should be done by trained personnel using proper
tools and procedures. Always read and understand any manufacturer's warning
contained in their customer's literature or molded into the tire sidewall.
Failure to
comply with these procedures may result in faulty positioning of the tire
and/or rim parts, and cause the assembly to burst with explosive force,
sufficient to cause serious physical injury or death. Never mount or use
damaged tires or rims.
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WARNING
Excessive
speed in a free-running, unloaded tire can cause it to "explode"
from extreme centrifugal force. The energy released by such an explosion
is sufficient to cause serious physical injury or death.
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TIRE
MAINTENANCE
When a tire is losing
air it must be removed from the wheel by an expert for complete internal inspection
to be sure it is not damaged. Tires driven even short distances while severely
underinflated may be damaged beyond repair.
Punctures up to 1/4"
in diameter, when confined to the tread, may be repaired by trained personnel.
These tires must be removed from the wheel, inspected and repaired using industry-approved
methods which call for an inside repair unit and a plug. Some punctures may
make the tire non-repairable. A plug by itself is an unacceptable puncture
repair.
The repair material
used -- for example, a "combination patch and plug" repair -- must
seal the inner liner and fill the injury to be considered a permanent repair.
Never use a tube in a tubeless tire as a substitute for a proper repair.
Individual tire manufacturers
may differ on whether the speed category applies to speed-rated tires that have
been repaired. Consult the tire manufacturer's policy.
Aerosol Inflators
Do not depend on
tire aerosol sealants and inflators to permanently fix a damaged tire. These
products are designed to provide only a temporary, emergency repair to help
get you off the road and to the nearest tire repair facility. They may also
make the tire non-repairable.
Some aerosol products
of this type use flammable gases, such as butane, propane or isobutane as propellants.
Follow all directions and precautions printed on the canister when using these
products. Be sure to inform tire service personnel when you have used any
flammable aerosol to inflate your tire.
Tire Rotation
The purpose of regularly
rotating tires is to prolong their useful tire life by achieving more uniform
wear for all tires on a vehicle. Before rotating tires, check your owner's manual
for rotation recommendations for specific vehicles. If no rotation period is
specified, rotate your tires every 6,000 to 8,000 miles or at any sign of uneven
wear. If the tires show uneven wear, ask a serviceperson to check for and correct
any misalignment, imbalance, or other mechanical problem before rotation.
Rotating the tires
as recommended by the RV or tire manufacturer will help even out the amount
of wear on each tire and extend the life of the entire set.
Note: Some
kinds of tires cannot be rotated in the manners described below. Such tires
include uni-directional tires and tires with asymmetric tread designs. Also,
some vehicles may have different-sized tires mounted on the front and rear axles,
and these different-sized tires have rotation restrictions. Check your owner's
manual, or with your tire dealer, for the proper rotation recommendations for
these special cases.
When tires are rotated,
the inflation pressures must be adjusted for the tire's new positions in accordance
with the actual loads on that wheel position. Underinflated or overinflated
tires may result in poor handling, uneven treadwear and increased fuel consumption.
Note: Lugnuts
should be properly torqued anytime a tire/wheel/rim assembly is re-installed
on the vehicle.
Recreation
Vehicle Tire Rotation Patterns
Vehicles With Dual Rear Wheels
(only where tires are same type & size)
Parking the RV
When parking your
RV for extended periods of time, it is important to make sure the vehicle is
as level as possible -- not only for convenience and comfort purposes, but also
to avoid tire overload due to weight transfers. On RVs without built-in leveling
devices, it is customary to "block" the low wheel positions.
Extreme caution must
be taken to ensure that the tires are fully supported when using blocks. The
load on the tire must be evenly distributed on the block and, in the case of
duals, evenly distributed on blocks for both tires. If this isn't done properly,
tires can be damaged, leading to premature sidewall fatigue and ultimate tire
failure.
The illustrations
below show the correct and incorrect blocking methods.
Storing the RV
When recreational
vehicles are out of service for long periods of time, they should be put on
blocks. Place the blocks under the axles so that tires bear no load during the
storage period. Also ensure that the tire/wheel assemblies are protected from
direct sunlight. Because inflation pressure will fluctuate with surrounding
temperatures, a slight, gradual air loss will typically occur over extended
periods. Be sure to inflate the tires, including the spare, to operating pressure
before returning to service.
Tire Storage
If you remove your
tires from the RV, store them in an area that is clean, cool, dry, dark and
well-ventilated with circulating air. Tires should be stored so that the tires
at the bottom of a stack retain their shape. Store tires whitewall-to-whitewall
to avoid staining. If outdoors, protect tires with an opaque waterproof covering.
Tire Dealer Assistance
When you have questions
about tires, consult your tire dealer. A dealer is the best source of general
information and professional service on tires. Have your dealer inspect your
tires periodically and otherwise assist you in maximizing your tire investment.
Dealers have service manuals, wall charts and other industry publications on
tire load and inflation, tire repairs and tire replacements. They can provide
any replacement tires your vehicle needs, balance your tires and properly repair
damaged tires which are repairable.
Tire Blocking
Methods
© 2001 Rubber
Manufacturers Association. All Rights Reserved.
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