- Accessory weight – The combined weight (in excess of those standard items which may be replaced) of the 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 that are 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 core 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 Vehicle Weight Rating (GVWR) – The maximum permissible weight of this fully-loaded vehicle.
- Gross Axle Weight Rating (GAWR) – The maximum permissible weight, including cargo, fluids, optional equipment, and accessories that can be safely supported by each axle.
- Hitch weight – The vertical trailer load is supported by the hitch ball.
- 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 inner liner 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 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.
- 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 that 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.
- Occupant distribution – The distribution of occupants in a vehicle.
- Open splice – Any parting at any junction of tread, sidewall, or inner liner 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, protective bands or ribs.
- Pin Weight – The vertical trailer load is supported by the kingpin of a fifth-wheel hitch.
- 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 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 normal diameter of the bead seat.
- Rim size designation – This means the rim diameter and width.
- Rim type designation – This means the industry’s or 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.
- Test rim – The rim on which a tire is fitted for testing, and may be any rim listed as appropriate for use with the 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.
- Tread wear indicators (TWI) – The projections within the principal grooves are 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 and dividing by two.
- Weather side – The surface area of the rim is not covered by the inflated tire.
- Wheel center member – In the case of a non-pneumatic tire assembly incorporating a wheel, a mechanical device that 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 the tire and the vehicle.
- Wheel-holding fixture – The fixture is used to hold the wheel and tire assembly securely during testing.
You may obtain the original copy of The National Highway Traffic Safety Administration (NHTSA) brochure from:
https://one.nhtsa.gov/cars/rules/TireSafety/ridesonit/tires_index.html