Determining Axle Capacity of Trailer with 12 inch Hub Drums and 6 Lug Bolt Pattern

Updated 08/28/2018 | Published 08/27/2018

Question:

I’ve got an axle under my trailer with no markings. It is 2.75 diameter round tube, has 6x5.5 hubs and 12” trailer brakes. All my research is finding the tube just under the 5k-7k axles and that’s what every axle I’ve seen with 12” brakes are rated. The 3500 axles all have 10”. Im looking at having it loaded right about 4000lbs overall gvwr

asked by: Chris

Expert Reply:

Sounds like you should be fine if that's what you are asking. Based on the hubs you have on the trailer I'd imagine you have the higher rated axle you mentioned.

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

Since you are at 2.75 inches in diameter you aren't going to fall under a standard capacity based on that alone, but your wheel bolt pattern and drum diameter dictates higher like 6k.

expert reply by: Jameson C