Determining Axle Capacity Based Off of the Axle Diameter

Question:

I read the threads on determining axle capacity based on diameter and its very insightful however are those specs axle shaft size or the tube?

asked by: Jeremy S

Expert Reply:

The measurements that you are referring to (listed below) are the actual diameter of the axle itself. By shaft size I am guessing you are referring to the spindle? The spindle actually doesn't go all the way through the axle as you can see when you look at a replacement spindle like part # TRU74FR.

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

Although the diameter is a really good indicator as to the weight capacity of your axle, the best thing to do is either find the capacity on the axle itself (typically located in the middle somewhere) or by contacting the manufacturer. It is better to take a few extra steps to keep from overloading your axles than to assume the weight capacity and create some potential dangerous situations.