How to Determine Capacity of Trailer Axle with 8 Lug Wheels

Published 08/29/2018

Question:

How do I determine the weight capacity on a boat trailer? It’s a dual axle, 8 lug, with 16” wheels. Not sure of axle diameter, as I’m not sure if it’s asking for the measurement for the outside diameter of the axle casing or not. Just want to make sure this trailer can handle my boat.

asked by: Chris O

Expert Reply:

If the trailer has 8 lug hubs that would indicate typically that the capacity for each axle is at least 5,200 lbs. Now if you go out and measure the outside diameter of the axle you'll get an even better idea.

Typical Axle Diameters Based on Axle Capacity
- 1,000-lb - 2,000-lb Axles: 1-1/2 inch - 1-3/4 inch diameter
- 3,500-lb Axles: 2-3/8 inch diameter
- 6,000-lb - 7,200-lb Axles: 3 inch diameter
- 8,000-lb Axles: 3-1/2 inch diameter
- 9,000-lb Axles: 4 inch diameter
- 10,000-lb Or more axles: 5 inch diameter

expert reply by: Jameson C