Series/Model:
Companies carry a variety of tires for various applications, depending on the needs of the driver.

Sidewall Abbrev.
XNW = Extra Narrow White Sidewall
BSL=Black Serrated Letters
BL=Black Lettering
WL=White Lettering
BW= Black Sidwall
WS=White Sidewall
RWL=Raised White Letters
BXS=Black Extra Narrow Segments
VSB=Vertical Serrated Band

Weight:
Weight of tire without inflation or rim.

Tire Size & Service Description (e.g. P185/70R13 89T):
 

• P   Tires with a P are using a P-Metric designation, which is the American market sizing standard started in 1976. All P-Metric tires are engineered to standards of T&RA (Tire and Rim Association). The "P" stands for "Passenger" vehicle. If there is no "P", the tire is engineered to ETRTO (European Tire and Rim Technical Organization) standards and is considered a metric tire. Standards by ETRTO and T&RA have evolved together, and are virtually interchangable.
• 185   The first number on the tire size is the cross-section width. This value is the width of the tire from side-wall to side-wall as measured in millimeters. This measurement is usually obtained from the bead of the tire (where the tire mounts to the rim.)
• /70   The two digit number just to the right of the slash (/) is what is referred to as the "aspect ratio". Not a 'specific length', this value describes the distance between the bead of the tire to the tread as compared to the cross-section width. This is viewed as a percentage value. (e.g. P185/70R13 has an aspect ratio of  70% of 185mm....or 129.5mm.). Lower apect ratios confer a stiffer ride and increased control than a similar sized tire with a larger aspect ratio. But larger aspect ratios tend to be more absorbant and add to a smooth road ride.
• R    This letter indicates the type of ply construction in the tire's casing or carcass. "R" means radial. "D" means diagonal, referring to bias tires. "B" means belted for belted-bias tires. Never mix radial tires with any other constru ction on a car.
• 13   Rim Diameter. It is the diameter of the bead seat in the rim. Most tires are built to inch standards for rim diameters. However, some tires are built to millimetric rim dimensions. Always match the tire's rim diameter to the wheel rim diameter.
• 89   Load capacity. Refer to the load index chart of a tire guide to find the maximum load carrying capacity of the tire.
• T  Speed Rating. This designation should be compared to the Speed Rating Chart to view the recommended maximum speed for this tire.

Overall diameter:
The diameter of an unloaded, inflated tire measured from the crown on one side to the crown on the opposite side. The free radius equals one-half the overall diameter. Sometimes called the outside diameter.

Overall Width:
This is the widest measurement of the tire from side-wall to side-wall. The width of tire buldge at full inflation.

Tread Width:
This is the width of tread, side to side, in inches that actually contacts the road suraface when tire has full inflation.

Static Load Radius:
The distance from the center of the axle to the ground under the specified load at full inflation.

Revs/Mile:
Revolutions per mile. The number of full rotations the wheel completes when a linear mile is travelled.

Tread Depth:
The depth of grooves and channels on the wheel's contact surface. Deeper tread depth permits water to drain away from the footprint, and may increase in traction on snow or soft surfaces.

Tread Wear Warranty:
The milage up to which the tires may be driven on and still covered by the manufacturer's warranty against defects.

UTQG Rating
UTQG is the Uniform Tire Quality Grading system.  It is a series of a number and two letters such as 320AB that represent the "3 T's" of tire grading: Treadwear, Traction and Temperature ratings. The treadwear grade is based on a standardized government test with a base index of 100.  A tire with a 320 treadwear rating would wear 3.2 times better than the government's "base" tire. The traction letter (A, B or C) represent the tire's ability to stop on wet pavement.   "A" tires have the best wet pavement traction in straight-ahead braking tests. The temperature letter (AA, A, B or C) represent the tire's ability to dissipate heat and resist heat
generation under controlled test.  "AA" tires have the best heat resistance.

Load Index Chart