How to Determine The Axle Weight Capacity On A 20 Foot Stock Trailer

Question:

I have a 20 stock trailer. How can I figure out what the axle rating is so I can choose the correct brake assembly. Are the 3500# brake assemblies the same dimensions #7000 assemblies? Thanks for your help

asked by: karl

Expert Reply:

The trailer will have a plate or sticker on it that will list the VIN number. The weight rating of the axle should be listed on that same plate or sticker. Also, the axle could have a tag or plate on it that will list the weight capacity.

You can also tell the weight capacity of the axle by measuring the diameter of the axle. A 3,500-lb. axle will have a diameter of 2-3/8 inches and a 6,000-lb. to 7,200-lb. axle will have a diameter of 3 inches. I am sending a link to an FAQ page on trailer suspensions and it will list the axle diameters for different axle weight capacities.

The brake assembly size is different on the 3,500-lb. axle and the 7,000-lb. axle. The 3,500-lb. axles will use a 10-inch brake assembly and a 7,000-lb. axle will use a 12-inch brake assembly. A 7,200-lb. axle and larger will use a 12-1/4 inch brake assembly.

To determine the size brake assembly you have, measure the diameter of the mounted brake shoe, the width of the lining, and the distance between the mounting holes on center. It may also help if you can determine the manufacturer of your brake. Once you have these measurements you can choose the correct assembly for your axle.

If you get the weight capacity of your axle and need help with choosing the correct brake assembly please feel free to contact me and I will help you choose the correct setup for your trailer.

I am sending a video link on replacing trailer brakes on a trailer.

expert reply by: Jeff D