When you’re looking to upgrade the wheels on your trailer or you need new trailer wheel hubs, you need to know the lug pattern to determine the correct size. Typical trailer wheel sizes range from 14-to-18-inch with 4 lug, 5 lug, 6 lug or 8 lug patterns. The lug pattern measures the diameter around the circle formed by the lugs on the wheel. Two numbers designate lug patterns, the first is the number of lugs on the wheel and the second is the distance measured across from each lug, or the diameter.

It is fairly simple to measure the lug pattern on trailer wheels. The only tool you need to measure the lug pattern on a trailer wheel is a ruler or tape measure. The technique you use to measure an even number lug pattern is different from the way in which you measure an odd number lug pattern.

To measure 4 lug pattern wheels, hold the end of the ruler or tape measure at the center of one lug. Extend the ruler directly across the center of the wheel to the adjacent lug or bolt to determine the measurement. An example of a measurement for a 4 lug pattern is stated as 4 on 4 (inches).

To measure 5 lug pattern wheels, hold the end of the ruler or tape measure to the center of one bolt. Extend the ruler directly across from the bolt to the space across from the bolt, located in the center of two bolts or lugs, to determine the measurement. You can also measure odd lug pattern wheels by placing the end of a tape measure at the back of one bolt, or the side nearest the edge, skip a bolt and expand the tape measure to the center of the next bolt to determine the measurement. Boat trailers, for example, commonly have a 5 lug wheel pattern with the lugs spaced 4.5 inches apart, and are stated as 5 on 4.5 (inches).

To measure 6 lug pattern wheels, place the end of a ruler or tape measure in the center of one lug or bolt. Extend the ruler directly across the center of the wheel to the adjacent lug to determine the measurement. An example of a 6 lug pattern measurement on a trailer wheel is 6 on 5.5 (inches).

To measure 8 lug pattern wheels, place the end of a ruler or tape measure on the center of one lug. Extend the ruler directly across the center of the wheel to the adjacent lug to determine the measurement. The general example for an 8 lug pattern measurement is 8 on 6.5 (inches).

You may hear of lug patterns, or the diameter, measured in mm. Convert inches to mm by using the formula 1-inch is equal to 25.4 mm.