BRAKE CLEARANCE (FIG. 2)
Starting from the center of the wheel hub, measure to the point where you make contact with the top fender wall.
Tip: Remember suspension travel as well as tire height must be factored into the rim sizing.
BACK-SPACING (FIG. 1)
The distance between the inner most fender wall and the wheel contact point of the mounting hub.
Tip: Also note the total depth of the wheel well and the depth from the hub to the closest piece of you wheel assembly.
Simply the diameter at the extremity of your brakes (A), be it discs or drums.
Tip: Measure the distance between the caliper and the hub (B) to ensure that there will be no friction with the wheel spokes.
BOLT PATTERN & SPACING (FIG. 3)
Note the number of mounting bolts. Measure the diameter of the imaginary circle which crosses those bolts are their center.
Tip: On a 5 bolt pattern, use the center of one bolt and the extremity of its diagonal to obtain the circle’s diameter.
Measure the diameter of the spindle that is protruding from the wheel hub.
Tip: For a quick and easy measurement, use a telescopic bore meter on the original wheels.
* These 5 steps establish the “fixed” confines to which your wheel set-up must adhere. They form the basis on which you will determine your rim and tire specifications—things such as diameter, width, and offset.