Bolt pattern

Discount Tire describes bolt patterns as a two-number system. The first number counts the wheel’s bolt holes; the second gives the diameter of the imaginary circle through their centers.

Summit Racing also calls this measurement the bolt circle or Pitch Circle Diameter (PCD). The diameter may be written in inches or millimeters, so keep the unit with the measurement.

Count the lugs before measuring. For 4-, 6- and 8-lug patterns, Discount Tire and Summit Racing describe a center-to-center measurement directly across the circle.

For neighboring studs, use this formula: bolt-circle diameter = distance between neighboring stud centers / sin (180° / number of studs). Enter the center-to-center distance in the tool and select the lug count; the result uses the same distance unit.

For 5x4.5 in, neighboring stud centers are 2.65 in (67.2 mm) apart by the formula. For 6x5.5 in, that distance is 2.75 in (69.9 mm), while 8x6.5 in gives 2.49 in (63.2 mm).

• 4-lug: measure between the centers of directly opposite holes.
• 5-lug: Discount Tire describes a backside-of-one-hole to center-of-the-third-hole estimate. It says accurate measurement requires a bolt-pattern gauge or geometric equation.
• 6- and 8-lug: measure between the centers of directly opposite holes.

Multiply inches by 25.4 to get millimeters. Convert only the circle diameter; the lug count stays unchanged.

By the formula, 5x4.75 in equals 5x120.65 mm, and 5x5 in equals 5x127 mm. Likewise, 6x5.5 in equals 6x139.7 mm.

The bolt pattern chart shows common inch and metric equivalents calculated by the formula. Some inch values are rounded: 5x112 mm is shown as 5x4.41 in, and 8x170 mm as 8x6.69 in.

Center bore, lug thread and seat type are separate specifications. A matching bolt pattern alone does not establish wheel compatibility.

Fit depends on the vehicle, wheels and suspension. Check rim size and wheel offset separately rather than treating the lug pattern as a complete wheel specification.

Discount Tire says never to install wheels that do not match the original-equipment bolt pattern, even when the measurements seem close. Summit Racing warns that a slightly different pattern can leave the wheel off-center and cause excessive vibration.