Tire Safety Information
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 nonpneumatic
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.
3.5 TIRE SAFETY - EVERYTHING RIDES ON IT
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:
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