B a s

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.