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Old 08-12-2017, 11:10 AM   #1
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Default Brake magnets ?

While crawling around under my new toy I noticed a broken wire behind the backing plate of one of the wheels. I know that it goes to a magnet on the inside and it needs to be replaced. I have never repaired electric brakes and have some drum brake experience.

Can I replace just one magnet or do they get replaced in pairs? Are they one size fits all? Are there junk parts or brands to avoid?

Please advise.

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Old 08-12-2017, 11:17 AM   #2
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Location: Colorado
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Here's a video on magnet replacement.

They're not one size fits all, they go by hub diameter and axle weight rating.

Good luck.

Replace both magnets on same axle. Probably wise to replace all 4 if you have 2 axles.

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Old 08-12-2017, 02:46 PM   #3
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Super video! Thanks, I can do that!
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Old 08-12-2017, 05:26 PM   #4
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Personally, I'd advise getting the complete assembly that includes new drums. This simplifies installation and they are not all that expensive. I get mine from E-Trailer.

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Old 08-15-2017, 07:50 AM   #5
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What Jack said.

Its almost easier to replace the hub than to repair - you have to disassemble down to the hub anyway, and replacement parts can easily have a new design thats ever so slightly different-just enough so it won't fit (mount bar is 1/16" wider, for example).

New hub is just four more bolts and two wire crimps (crimps you have to do with a repair anyway).

I once converted a surge brake trailer to electric for lower cost and less time than repairing the hydraulics. Thats how easy electrics are.
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Old 10-21-2017, 07:45 PM   #6
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Sounds like all you needed to do was repair the broken wire. Why did a broken wire lead you to believe you needed to replace the magnet or the entire assembly, as some suggested?
Magnets will wear out. The way they work is when a current is applied they become magnetic (copper wire wound around a circle is magnetic when electrified). When it is magnetic the magnet is attracted to the steel brake drum. When the magnet sticks (via magnetism) to the drum it drags and pulls the brake mechanism into action. That action pushes the brake pads against the braking surface. The more electricity is applied the more magnetic/stronger the magnet becomes and thus it sticks to the brake drum more which pulls harder and harder on the brake mechanism. - thus harder braking with more current. Current is dictated from the brake controller at your knee.
The magnet is dragging on the brake drum as much as the brake pads are so they wear out. They are pretty generic, but there are different sizes within this generic range. I have not heard of any bad brands.
Complete assemblies are pretty inexpensive and I have replaced all 4 brakes instead of fiddling with magnets or possibly broken or worn brake assemblies/ trouble shooting, but would have fixed the wire first in this situation…

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