Do Brake Magnets Need To Sit Perfectly Flat on Inside Armature Surface of Brake Drums

Updated 08/15/2020 | Published 08/12/2020

Question:

Hello, How smooth does the surface of the drum need to be for the magnet to properly work. Would the magnet portion be able to be turned. Magnet portion is small ripples...not bad, its just not 100 flat. Have replaced both brake assemblies, wiring from front to back and side to side, new brake controller and still the brakes are not applying completely. They are adjusted out.

asked by: Eric

Expert Reply:

In order for the trailer brake magnets to get full adhesion to the inside armature surface of the brake drum, the magnet face and the armature surface of the drum need to be perfectly flat and smooth. Since they aren't mating together perfectly, it's possible that this is could cause the braking problem you describe. You'll also want to make sure that the ground connection for each magnet is securely attached to clean, bare metal.

Since it seems that you've eliminated everything else, your hub/drums seem to be the only likely remaining culprit. Eventually, the surface of the magnet will wear down to conform to the grooves on the armature surface but you'll continue to experience diminished braking performance until things 'wear in', so replacing the drum is recommended.

expert reply by: Mike L