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3. Tire Safety Information
This portion of the User's Manual contains tire safety
information as required by 49 CFR 575.6.
Section 3.1 contains "Trailer Tire Information".
Section 3.2 contains "Steps for Determining Correct
Load Limit - Trailer".
Section 3.3 contains "Steps for Determining Correct
Load Limit – Tow Vehicle".
Section 3.4 contains a Glossary of Tire Terminology,
including "cold infl ation pressure", "maximum infl ation
pressure", "recommended infl ation pressure", and
other non-technical terms.
Section 3.5 contains information from the NHTSA
brochure entitled "Tire Safety – Everything Rides On
It".
This brochure, as well as 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 Identifi cation Number (TIN).
• Recommended tire infl ation pressure, including a
description and explanation of:
A. Cold infl ation pressure.
B. Vehicle Placard and location on the vehicle.
C. Adverse safety consequences of under infl ation
(including tire failure).
D. Measuring and adjusting air pressure for proper
infl ation.
• 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 confi gurations 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.
Tire Safety
3.1 Trailer Tire Information
Trailer tires may be worn out even though they still have
plenty of tread left. This is because trailer tires have to
carry a lot of weight all the time, even when not in use.
It is actually better for the tire to be rolling down the road
than to be idle. During use, the tire releases lubricants
that are benefi cial to tire life. Using the trailer tires often
also helps prevent fl at spots from developing.
The main cause of tire failure is improper infl ation.
Check the cold tire infl ation pressures at least once a
week for proper infl ation levels. "Cold" means that the
tires are at the same temperature as the surrounding air,
such as when the vehicle has been parked overnight.
Wheel and tire manufacturers recommend adjusting the
air pressure to the trailer manufacturer's recommended
cold infl ation pressure, in pounds per square inch (PSI)
stated on the vehicle's Federal Certifi cation Label or Tire
Placard when the trailer is loaded to its gross vehicle
weight rating (GVWR).
If the tires are infl ated to less than the recommended
infl ation level or the GVWR of the trailer is exceeded, the
load carrying capacity of the tire could be dramatically
affected. If the tires are infl ated more than the
recommended infl ation level, handling characteristics
of the tow vehicle/trailer combination could be affected.
Refer to the owner's manual or talk to your dealer
or vehicle manufacturer if you have any questions
regarding proper infl ation practices.
Tires can lose air over a period of time. In fact, tires can
lose 1 to 3 PSI per month. This is because molecules of
air, under pressure, weave their way from the inside of
the tire, through the rubber, to the outside. A drop in tire
pressure could cause the tire to become overloaded,
leading to excessive heat build up. If a trailer tire is
under-infl ated, even for a short period of time, the tire
could suffer internal damage.
High speed towing in hot conditions degrades trailer tires
signifi cantly. As heat builds up during driving, the tire's
internal structure starts to breakdown, compromising
the strength of the tire. It is recommended to drive at
moderate speeds.
Statistics indicate the average life of a trailer tire is
about fi ve years under normal use and maintenance
conditions. After three years, replacing the trailer tires
with new ones should be considered, even if the tires
have adequate tread depth. Some experts claim that
after fi ve years, trailer tires are considered worn
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