Determining Trailer Hub & Drum Bolt Patterns
How to Measure Trailer Hub & Drum Bolt Patterns
Understanding your trailer’s bolt pattern is essential when selecting the right hub or drum. This quick-reference guide from PTC helps you accurately measure bolt patterns across 4-, 5-, 6-, 8-, and 10-lug configurations so you can find the right parts fast.
Step 1: Count the Number of Studs
Start by determining how many bolt holes (studs) are on the hub—most common patterns include 4, 5, 6, 8, or 10-lug designs.
Step 2: Measure the Bolt Pattern
The method you use depends on whether the hub has an even or odd number of studs:
- Even Number of Studs: Measure center-to-center across from two opposing studs (e.g., “8 on 6-1/2” means 8 holes spaced across a 6.5” diameter).
- Odd Number of Studs: Measure from the center of one stud to the midpoint between two studs directly across from it.
Alternative 5-Lug Measuring Method:
Another way to measure a 5-lug pattern is to measure the distance between the centers of two adjacent studs. Use the chart below for reference:
- 5 on 4-1/2″ = 2-5/8″ between studs
- 5 on 4-3/4″ = 2-3/4″
- 5 on 5″ = 2-7/8″
- 5 on 5-1/2″ = 3-1/4″
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