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NHTSA Trailer Equipment Requirements
Tread means that portion of a tire that comes into contact
with the road.
Tread rib means a tread section running circumferentially
around a tire.
Tread separation means pulling away of the tread from
the tire carcass.
Treadwear indicators (TWI) means the projections within
the principal grooves designed to give a visual indication
of the degrees of wear on the tread.
Vehicle capacity weight means the rated cargo and
luggage load plus 68 kilograms times the vehicle's
designated seating capacity.
Vehicle maximum load on the tire means that 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 means that 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 49 CFR 571.110) and dividing by two.
Wheel center member means, in the case of a
nonpneumatic tire assembly incorporating a wheel, a
mechanical device which attaches, either integrally or
separably, to the nonpneumatic rim and provides the
connection between the nonpneumatic rim and the
vehicle; or in the case of a nonpneumatic tire assembly
not incorporating a wheel, a mechanical device which
attaches,
either
integrally
nonpneumatic tire and provides the connection between
the tire and the vehicle.
Wheel-holding fixture means the fixture used to hold the
wheel and tire assembly securely during testing.
Tire Safety
The National Traffic Safety Administration (NHTSA) has
published a brochure (DOT HS 809 361) that discusses
all aspects of Tire Safety, as required by 49 CFR 575.6.
This brochure is reproduced in part below. It can be
obtained and downloaded from NHTSA, free of charge,
from the following website:
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
40
or
separably,
to
the
•
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.
Basic Tire Maintenance
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.
Finding Your Vehicle's Recommended Tire Pressure
And Load Limits
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.
Understanding Tire Pressure And Load Limits
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
Owner's Manual for Mobile Generator Sets
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