How to Replace Manual Adjusting Trailer Brake Assemblies with Self Adjusting Assemblies

Published 11/25/2015

Question:

I am wanting to replace my old stock trailer electric brakes with new assemblies that auto adjust. How do I determine what size I need. I know I can measure the drum, but you mention about axle rating. How do I determine my axle rating? Also, would you recommend new bearings they were replaced not too long ago but if they are not too expensive and come pre-greased I would want to get them and what other items grease seals, etc might I need from you to get the job done? Thank you.

asked by: Stan

Expert Reply:

To determine what brake assemblies you would need will require you to measure the inner diameter of the drum hubs as well as the depth like in the picture I attached. I attached a page that has all of our self adjusting brake assemblies for you to check out once you know those dimensions.

To determine the axle capacity you can do it a couple ways. There should be a plate or sticker near the tongue of the trailer that will have the overall trailer capacity as well as axle capacities. You may also find this info on a similar plate on the axle. Or you can measure the diameter of the axles to determine this.

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 going to have to remove the hub you might be interested in replacing the bearings, but if they are pretty new and are seemingly fine I would probably not only because removing the hub to change assemblies does not require removing the bearings or seal. The hub will slide right off with the bearings and seal inside. The bearings do not come pre-greased either.

However I attached a video on replacing bearings and seals to show you what it takes in case you do decide to go ahead and change them.