Proper size and load range is crucial when selecting new trailer tires, in order to match the proper load requirements of the trailer. The following characteristics are extremely important and should be thoroughly checked when replacing trailer tires. The following are the characteristics to look at closely: TIRE CONSTRUCTION TYPE - Bias Ply vs. Radial TIRE APPLICATION TYPE - (ST) Special Trailer vs. (P) Passenger Car TIRE SIZE - % of section height / section width Refereed to as 'Aspect Ratio' TIRE LOAD RANGE - Load carrying capacity and air pressure rating RIM SIZE - Diameter and width must match tire RIM BOLT CIRCLE - Diameter of bolt circle must match hub
There are three different identification systems that the trailer tire industry uses. All you need to do is look on the side wall of the tire you have to match up what you buy. The three systems are as follows: THE NUMERIC SYSTEM - (4.80 X 8) mostly used on smaller trailer tires, indicates the tire section width (4.80"), and the rim diameter (8") THE ALPHA NUMERIC SYSTEM - (B78 X 13 C) common on 13"-15" trailer tires, indicates air chamber size (B), the 'Aspect Ratio' (78), the rim diameter (13"), and the load range (C) THE METRIC SYSTEM - (ST205 75D 15) currently being phased in by trailer tire manufacturers, indicated the tire application type (ST-special trailer), the section width (205mm), the 'Aspect Ratio' (75), the construction type (D= bias ply), and rim dia.(15")
To make the tire work properly with your trailer, you also need the correct rim to go with that tire. Doing so will assure that your existing trailer hardware will work with the replacement tire and rim. Be certain to match the bolt pattern on the hub. It usually consists of either a 4 bolt or 5 bolt pattern.
You must also consider the maximum weight that each tire can support, or 'load range'. The load range and maximum weight capacity are indicated on the tire side wall. LOAD RANGE B = OLD 4 PLY RATING LOAD RANGE C = OLD 6 PLY RATING LOAD RANGE D = OLD 8 PLY RATING