Brake magnets causing groove in hubs

[bob213]

Doing a bearing repack. Left side hubs were much tighter against brakes. Looks like magnet has rubbed against hub and caused a groove. Magnet looks worn down as well. Brakes have been working fine as far as I know. Suggestions????

[kfergiez]

This is actually what they're supposed to do.

The magnets grab the inside of the drum, this forces a lever to move which spreads the shoes and slows the trailer.

The magnet and that section of brake drum are wear items just like the shoes.

[MR.M]

Originally Posted by bob213

Doing a bearing repack. Left side hubs were much tighter against brakes. Looks like magnet has rubbed against hub and caused a groove. Magnet looks worn down as well. Brakes have been working fine as far as I know. Suggestions????
Attachment 197886

Attachment 197887

Attachment 197888

I would replace the whole brake backing plate with all new . they come complete , shoes , magnets , etc all assembled just bolt on . i would not reassemble what you have and expect it to work

[kfergiez]

Originally Posted by MR.M

I would replace the whole brake backing plate with all new . they come complete , shoes , magnets , etc all assembled just bolt on . i would not reassemble what you have and expect it to work

This is how they are SUPPOSED to wear. It will work just fine as long as they are within spec.

You need to follow the instructions in your manual to measure the drum, and wear on your magnet. If they are within spec you'll be fine.

[kfergiez]

Here is a VERY good video on how these operate:

https://www.youtube.com/watch?v=S1oTeUADBMM

[babock]

Buy a new magnet and a new drum.


Perfect example why you pull your drums yearly.

[bob213]

Thank everyone. I don't think they look much different than video. I may replace magnet to be sure.

[Larry-NC]

Originally Posted by babock

Buy a new magnet and a new drum.

Why would you do that without measuring wear? Those friction marks will come up the very first time you brake. Maybe even while you are setting the brake controller as you pull out on the trip, one block from your house.

You wouldn't change the pads or shoes on your car after making one stop, would you?

Originally Posted by babock

Perfect example why you pull your drums yearly.

Even changing brakes after one year doesn't make sense if they aren't worn below spec.

Larry

[babock]

Originally Posted by Larry-NC

Why would you do that without measuring wear? Those friction marks will come up the very first time you brake. Maybe even while you are setting the brake controller as you pull out on the trip, one block from your house.

You wouldn't change the pads or shoes on your car after making one stop, would you?


Even changing brakes after one year doesn't make sense if they aren't worn below spec.

Larry

Take look at the groove in the magnet along with the corresponding groove in the drum. It should be perfectly smooth. A new magnet will get worn out prematurely. If a machine shop can plane that brake area, then that would be sufficient.

I NEVER said change the brakes every year but to pull the drum yearly to inspect.

[Filterman]

Originally Posted by kfergiez

This is how they are SUPPOSED to wear. It will work just fine as long as they are within spec.

You need to follow the instructions in your manual to measure the drum, and wear on your magnet. If they are within spec you'll be fine.

X2 yes that’s the wear point in any electric brake.