Tires: Definitions

This glossary includes key terms from the Guide and may be used as a companion to the text.

Alignment	adjusting the angle of a vehicle's tires so that they are perpendicular to the road and parallel to each other.
All-season tires	tires designed for use across a range of weather conditions rather than for a particular type of weather (e.g., winter tires).
Balancing	adding of wheel weights to tires to compensate for imperfections resulting from the manufacturing process.
Dioxins	chemical compounds classified as persistent, bioaccumulative, and toxic (PBTs) by the EPA.
End-of-life management	process by which products are disposed of after their term of useful service expires.
Energy efficient	product that performs more work per unit of energy as compared to all similar products.
Hazardous substance	1. material posing a threat to human health and/or the environment, that can be toxic, corrosive, ignitable, explosive, or chemically reactive, 2. substance that must be reported to the EPA if released into the environment.
High-performance tires	tires designed for higher speeds and greater traction. Typcially have higher rolling resistance than other types of tires.
Lead	soft, heavy metal used in tire wheel weights that can cause brain and kidney damage when ingested.
Lead-free wheel weights	wheel weights made of materials other than lead, such as steel, zinc, and plastic.
Low rolling resistance (LRR) tires	tires that improve vehicle fuel efficiency by reducing rolling resistance. LRR tires come standard on most new vehicles but are not not widely marketed as replacement tires.
LRR tires	see "Low rolling reistance (LRR) tires"
OEM tires	tires sold as original equipment on new vehicles. Often OEM tires are LRR tires.
Recapped tires	see "Retread tires"
Replacement tires	tires purchased to replace OEM tires.
Retread tires	used tires with core structure still intact and a new layer of rubber tread applied using similar techniques to OEM tire manufacture. Light-duty retread tires require 2 to 3 gallons of oil to produce whereas new light-duty tires require 7 to 8 gallons.
Rolling resistance	the amount of contact between tires and the road surface. Rolling resistance is influenced by tire inflation and design, vehicle load and speed, and road surface. Each 10% reduction in rolling resistance improves vehicle fuel economy by 1-2%.
Rolling resistance co-efficient (RRC)	quantitative measure of a tire's rolling resistance. RRCs for new tires are typically between 0.007 and 0.014 (NAS, 2006), with a lower number representing a lower rolling resistance. An LRR less than 0.0105 can be considered "low" rolling resistance (Green Seal, 2003).
Rotation	periodic movement of tires to new wheel positions to promote even wear.
Run-flat tires	tires with reinforced sidewalls that allow the vehicle to continue traveling at speeds upwards of 40 mph for a limited distance even with no inflation.
SAE 1269	widely accepted rolling resistance testing procedure designed by the Society of Automotive Engineers.
Speed rating	speed at which a tire can safely operate.
Steel	hard, strong allow of iron and carbon that can be used as a substitute for lead wheel weights. Steel can corrode when exposed to water and air, thus steel wheel weights typically require a thin coating of zinc or plastic.
Tread	grooved surface of a tire that can vary in depth and pattern based on tire design.
VOC	see "volatile organic compounds"
Volatile organic compound (VOC)	organic compound that typically vaporizes at room temperature and participates in atmospheric photochemical reactions.
Wheel weight	blocks of heavy material, typically lead, affixed to tires for balancing. Each light-duty tire typically has 4.5 ounces of lead clipped to it. Around 2,000 tons of lead wheel weights fall off of vehiles each year in the United States.

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