Basic Tire Facts In an effort to clarify the confusion in tire sizing we offer the following: Lawn and Garden, Industrial, ATV and Go-Kart Tires There are two methods of identifying tires in this category: Overall Diameter x Section Width x Rim Diameter. An example of a L&G tire size is 13/6.50-6. An ATV tire size is 22/1100-8. Section width x section height x rim diameter An example of this type of tire is 5.30/4.50-6. Bicycle, Lawn Cart and High Wheel Mower Tires Overall diameter x section width An example of this tire size would be12x1.75 Trailer Tires Like Lawn and Garden, Industrial and Go-Kart tires, there are several ways to identify tires in this category Overall diameter x Section Width x Rim Diameter An example of this tire would be a 16.5x6.5-8; this type of tire is normally used on camper, snow mobile and lawn equipment trailers. Section Width x Section Height x Rim Diameter An example of this type of tire would be the 480/400-8. This is an older size designation. It is generally used for the smaller 8” and 12” rim sizes. In recent years 13, 14 and 15” trailer tires have been sized using a metric format. Trailer tires in these sizes are produced in radial or bias ply construction, they are measured as follows. Section Width x Aspect Ratio x Rim Diameter An example of this size would be the ST205/75R15 ST = Special Trailer 205 = Section Width stated in millimeters 75 = Aspect Ratio is the ratio of Section Height to Section Width R = Construction Code: R=Radial, D=Diagonal or Bias Ply ` 15 = Rim Diameter Basic Tire Definitions Ply Rating An index of the tires strength; ply rating indicates the maximum recommended load for specific types of service. Ply rating normally does not indicate the number of plies or layers in the tire. Load Range Used to identify a tires load and inflation limits when used in a specific type of service. Load Ranges are signified by a letter (A, B, C etc.). Bead width The distance between the vertical portions of the rim flange. If the rim is too wide or narrow, the tire will not seat properly. As a rule, bead widths should be ½” to 1 ½” narrower than the section width of the tire to provide for a proper fit. Section Width The distance across the tire at its widest part when inflated but not under load. Section Height The distance between the top of the tire and the bead seat when the tire is inflated but not under load. Overall Diameter The distance from the top to the bottom of the tire when it is inflated but not under load Basic Rim Facts Slow Speed Rims Slow Speed Tire/Wheel Assemblies and Rims represent the largest proportion of the small wheel business. Slow Speed Wheels are found on everything from children’s wagons, to wheel barrows, hand trucks, outdoor power equipment, casters and industrial trailers. When ordering slow speed wheels you will need to know a few items: Tire size Tire Ply Rating Tire – tubeless or tube-type Hub length – what is the overall length of the wheel hub from bearing to bearing. Hub offset – is the hub centered or is it offset. If offset what is distance from the center of the rim to the rim to the end of the hub tube in the male (non-valve stem) side. Bearing Style – what bearing style do you require, ball bearings, bushings, open cage roller bearings. Bearing Size – what is the outside diameter of the axle? Zerk Fitting – does the wheel require a zerk fitting. High Speed Rims High Speed Trailer Rims are designed specifically to handle the normal “wear and tear” of trailer use. When selecting trailer rims some thought must be given to the load that is to be carried. As a rule of thumb, overall capacity is limited by the component with the lowest capacity or the capacity of a standard axle. How to Determine a Bolt Circle Rims should be matched to hubs by the number of bolts and bolt circle. On rims with an even number of bolts holes, measure center to center on bolt holes directly across the pilot hole from one another. If the rim has on odd number of bolt holes measure from the center of one bolt hole to a position directly across the pilot to point hole half way between the two bolt holes most directly opposite from it. How to Determine Rim Offset Positive offset - the hub mounting face is to the outward side of the rim, the tire will be closer to the trailer frame. Negative offset - the hub mounting face is to the inward side of the rim, the tire will be farther away from the trailer frame.