- ST: Special Trailer Tire.
- ST tires are built with reinforced sidewalls and unique chemistry to handle the higher shear loads and longer storage periods of trailer service.
- 205: The section width in millimeters.
- 75: The aspect ratio, expressed as a percentage of the section width.
- R15: The size of the rim the tire is designed to be mounted upon.
- Some common trailer sizes are 5.30×12, 175/80-13, 205/75-14, and 205/75-15.
- Trailer tires larger than 16-inch are uncommon and reserved for extremely heavy loads. Almost all trailer suspension components (e.g hubs, brakes, etc.) are designed either for 8–12-inch tires (mini trailers, boat trailers) or 13–15-inch tires (utility trailers, small campers, etc.)
- Many tires will fit a small range of rim widths. For example, in this case, this tire might fit a 15×5-rim and a 15×5.5-inch rim. It depends on the section width.
- Hot hint! The most common wheel bolt pattern is 5×4-½. It’s available on virtually every common tire size from 12- to 15-inches. Smaller tires may use a 4×4 bolt pattern; tires with heavier load ranges may use 5×5.
- R: Indicates tire construction type.
- R: Radial-ply tire construction. More expensive construction, but preferred for highway service due to reduced heat buildup, low road noise, etc.
- D: Bias-ply tire construction. Less expensive, sturdy, preferred for about-town utility trailer use.
- LRD: The load range (commonly B, C, D, E, etc.) in lbs at a specific inflation pressure. Please see a tire Load Range chart to see specific values.
- Load range values are only commonly across a tire size. A 13″ LRD tire, for instance, will have a lower capacity than a 14″ LRD tire.
- Some tire labels will also feature a speed rating like “L” or “M.”
- The lack of a speed rating would indicate that the tire is rated for 65 mph.
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