The information stamped on the side wall of a trailer tire provides specific information regarding the size and style of the tire. This article will help guide you in reading it.
Steps
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For example, the tires on a boat trailer may be labeled ST175/80D13C.
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The ST means that these tires are Specialty Tires for trailer use only.
Specialty tires (ST) should never be used on cars, vans, or trucks.
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Next the number 175 means the maximum width of the trailer tire is approximately 175 millimeters at widest point.
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The number 80 indicates the height of the sidewall is 80% of the width, in this case 140 millimeters.
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The letter D shows that this is a bias tire, this means diagonal.
The belts on this tire run diagonally from bead to bead or at about 45 degree angles to the center line of the tire. If your tire shows the letter R, your tire is a radial tire. The belts on this tire run radially from bead to bead or at 90 degree angles to the center line of the tire.
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The number 13 indicates this trailer tire fits on a 13 inch (33.0 cm) diameter wheel.
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The letter C is the load index or load range, this could also be labeled with a ply rating.
Typically a “C” load range is equivalent to a 6 ply rated tire, “B” is a 4 ply, “D” is an 8 ply and “E” is a 10 ply rating.