How to Measure Trailer Wheel Bolt Pattern — All 5 Patterns with Diagrams

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Quick Answer

Count the lug studs first — that's half the answer. For even-lug patterns (4, 6, 8), measure center-to-center straight across two studs directly opposite each other. For 5-lug patterns, measure from the outer edge of one stud to the center of the stud two positions away. Write it as "lugs on diameter" — example: 5 on 4.5".

How to Measure — Even vs. Odd Lug Patterns

The Rule

Even number of lugs (4, 6, 8): Measure center-to-center directly across two opposite studs. This gives you the bolt circle diameter directly.

Odd number of lugs (5): You cannot measure straight across — there is no stud directly opposite. Instead, measure from the outer edge of one stud to the center of the stud two positions away (skip one stud). This measurement equals the bolt circle diameter.

All Five Trailer Bolt Patterns — Diagrams and Instructions

4 on 4.0"

2,000 lb axles · Small utility & boat trailers

Measurement MethodMeasure center-to-center straight across two studs directly opposite each other. With 4 studs at 90° intervals, any pair of opposite studs works.

Diameter: 4.0" · Studs: 4 · Spacing: 90° apart

Common on: 2,000 lb axles, small boat trailers, utility trailers under 2,200 lb

5 on 4.5"

3,500 lb axles · Most common trailer pattern

⚠ 5-Lug Measurement MethodMeasure from the outer edge of one stud to the center of the stud two positions away (skip one stud). Do NOT measure center-to-center — there is no stud directly opposite on a 5-lug hub.

Diameter: 4.5" · Studs: 5 · Spacing: 72° apart

Common on: 3,500 lb (#84 spindle) axles — most common trailer axle in the US

5 on 5.0"

3,500–5,200 lb axles · Less common variant

⚠ 5-Lug Measurement MethodSame as 5 on 4.5" — measure from the outer edge of one stud to the center of the stud two positions away. Looks identical to 5 on 4.5" to the eye — confirm with a tape measure. A 4.5" wheel will NOT fit a 5.0" hub.

Diameter: 5.0" · Studs: 5 · Spacing: 72° apart

Common on: Some 3,500–5,200 lb Lippert and Dexter axle variants. Confirm before ordering.

6 on 5.5"

5,200–6,000 lb axles · Mid-duty tandem trailers

Measurement MethodMeasure center-to-center directly across two studs directly opposite each other. With 6 studs at 60° intervals, every stud has one directly opposite. Any opposing pair gives the same reading.

Diameter: 5.5" · Studs: 6 · Spacing: 60° apart

Common on: 5,200–6,000 lb axles, mid-duty tandem axle utility and cargo trailers

8 on 6.5"

7,000–8,000 lb axles · Heavy dump trailers & equipment haulers

Measurement MethodMeasure center-to-center directly across two studs directly opposite each other. With 8 studs at 45° intervals, every stud has one directly opposite. Any of the 4 opposing pairs gives the same reading.

Diameter: 6.5" · Studs: 8 · Spacing: 45° apart

Common on: 7,000–8,000 lb axles — dump trailers, heavy equipment haulers, tandem axle heavy-duty trailers

Also used on: Some 3/4-ton and 1-ton trucks — do not assume a truck 8-lug wheel fits a trailer axle; thread pitch and hub bore may differ

Quick Reference Table

Pattern	Studs	Measurement Method	Typical Axle Capacity
4 on 4.0"	4	Center → Center (straight across)	2,000 lb
5 on 4.5"	5	Outer edge → Center (skip one stud)	3,500 lb — most common
5 on 5.0"	5	Outer edge → Center (skip one stud)	3,500–5,200 lb variants
6 on 5.5"	6	Center → Center (straight across)	5,200–6,000 lb
8 on 6.5"	8	Center → Center (straight across)	7,000–8,000 lb

⚠ 5 on 4.5" vs. 5 on 5.0" — They Look Identical

A 5 on 4.5" wheel and a 5 on 5.0" wheel look almost exactly the same at a glance. The only reliable way to tell them apart is to measure. A 5 on 4.5" wheel will fit on a 5 on 4.5" hub with zero play. A 5 on 5.0" wheel forced onto a 5 on 4.5" hub will sit crooked — the lug holes won't align. Always measure both the hub AND the replacement wheel before ordering.

Not sure which pattern you have? Call us and we can help identify it.

AAA Trailer: (517) 225-1991 | Howell, MI | aaatrailer.com