Adding Electric Brakes To A Car Dolly Trailer Without Brakes

Published 12/14/2021

Question:

Can I add brakes to a car dolly that came without brakes?

asked by: Dennis R

Helpful Expert Reply:

Yes, you can definitely add brakes to your car dolly. I recommend installing electric brakes as they more cost effective and provide the most stopping power for your application.

To add electric brakes to your tow dolly you'll need to know the bearing size and bolt pattern of the brake flange. Most likely you have a 4 bolt pattern brake flange which would mean you likely have a 3,500lb axle but we would still want to be sure.

The easiest way to determine which bearings are used on your trailer axle is to take the idler hub off and check for the numbers stamped into the bearings. If the bearing numbers cannot be read, the next best solution is to find the bearings' inner diameter and outer diameter. You'll need to use some calipers like the # PTW80157 to measure the inner diameter and out diameter of both bearings. If your bearings are damaged you can also measure the spindles at the inner (C in diagram) and outer (D in diagram) bearing surfaces as well as the seal contact surfaces (B in diagram).

I've attached an article that goes over typical bearing numbers with there dimensions listed in a chart but I can verify the bearing if you send in the dimensions as well.

Once we know the bearings and bolt pattern of the brake flange we can find the respective electric brakes and hubs/drums and then move on to the electrical components of this setup which include trailer wiring, a breakaway kit, and a brake controller.

expert reply by: Kevin C