| Term | Definition |
| ALPHANUMERIC SYSTEM |
A tire sizing system originally used in the late 1960’s. With this system, the tire’s load-bearing capacity, construction type, aspect ratio, and rim diameter could be determined at a glance. Example: BR78-13. The first letter, “B” is the load rating. The closer the letter to the end of the alphabet, the larger the tire size. “R” was added to the system as Radial tire construction began prevalent. “78” identifies the aspect ratio. “13” identified the wheel size, in inches. The alphanumeric system does not provide a way to identify the section width or overall diameter of the tire. See ASPECT RATIO, METRIC SYSTEM, MILLIMETRIC SYSTEM, P-METRIC SYSTEM, ISO METRIC
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| ANTI-OXIDANTS |
Anti-oxidants are molecular structures used to slow or prevent the oxidation (i.e, breakdown or degradation), of other molecules. They have many industrial applications including the prevention of oxidative degradation of rubber, that causes a loss of strength and flexibility.
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| ARAMID |
A synthetic fiber used in belt packages that is, pound for pound, nine time stronger than steel, although bulkier than steel. Generally limited for use in low heat, high centripetal force applications. Kevlar is an aramid material.
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| ASPECT RATIO |
The ratio of a tire’s cross section height (the distance between the rim and tread), to its width. The ratio is expressed as a percentage. The lower the aspect ratio of the tire, the smaller the height of the sidewall.
Example: P205/70R15 – the aspect ratio is 70. In this example, the cross section height is 70% of the tire’s width.
To calculate the actual cross section height, multiply … 205 mm x .70 = 143.50 mm.
To convert from millimeters to inches, multiply … 143.50 x .0397 = 5.7 inches.
To convert to a full tire height in inches … 5.7 + 5.7 + 15 (rim size) = 26.4 inches.
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| ASYMMETRIC |
A tread pattern that differs on either side of the tire’s centerline. Asymmetric tires are not reversible on a rim. Mounting of an asymmetric tire should reflect the inside or outside as marked on its sidewall. Asymmetric tires can also be “directional,” meaning that they can only roll in one direction.
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