How to Determine the Diameter of a Trailer Axle

Question:

I need a conversion kit to raise the trailer I just bought. I am trying to figure out which size axles I have. If I measure the current distance across the U bolts it is 2 5/8. I am assuming I have the 2 3/8 axle is this correct?

asked by: Larry

Expert Reply:

Measuring a round axle can be difficult. You would need a set of dial or digital calipers to get an accurate measurement. Using a tape measure would not be accurate enough. Calipers are available at discount tool shops. Nicer ones can get a little costly. But if you don't need precise measurements of things often an inexpensive analog model will work just fine.

Sometimes you can go by the axle capacity but not always.

Typical Axle Diameters Based on Axle Capacity

1,000-lb - 2,000-lb Axles: 1-1/2" - 1-3/4" diameter
3,500-lb Axles: 2-3/8" diameter (can have a 3-1/2" diameter, but rarely)
6,000-lb - 7,200-lb Axles: 3" diameter
8,000-lb Axles: 3-1/2" diameter
9,000-lb Axles: 4" diameter
10,000-lb Or more axles: 5" diameter

expert reply by: Michael H