Trailer brake tech

patooyee · May 24, 2015

I have two trailers and know virtually nothing about maintenance of trailer brakes. I suspect both need a little TLC in the brake department though. My bigger trailer has 10k oil bath axles and one of the seals went bad so I took it apart the other day thinking I would just get the part number off the existing seal, run down to Napa and grab a new one. WRONG! Everything on these axles are big truck parts and it is all strictly mail order unless you have a big truck parts store near you. The seal I need is a 10-56 unitized seal and is crazier than any seal I have ever seen before. So lesson #1 learned is to plan ahead!

Part of planning ahead requires knowing what's inside the axles before you tear them down. Or at least being prepared to tear down and park it until you can get parts there. The easiest way to do this is to find your factory service manual. After a ton of searching here is mine:

http://www.al-ko.us/download/ALKO_8kto16k_OwnerManuals.pdf

My understanding is that Al-Ko was one of the largest trailer axle manufacturers, if not the second largest, before they were bought by Dexter, which is the largest. I am told that many Dexter and Al-Ko parts interchange. How much truth there is behind that I don't know or care.

I have the 10k heavy duty drum brake version. Having never looked inside an electric drum brake I figured it would have been crazy-complex. But its actually not. There's just an electro-magnet that sticks to a plate called the armature plate that is bolted to the inside face of the drum when it is powered up. That magnet is attached to a lever / arm that goes from the bottom of the drum to the top. It has a slipper block attached to the top which pushes the brake shoes outward as the lever moves. The movement is achieved by the magnet getting drawn along the armature plate as the drum spins. Pretty simple once you see it all.

The magnet does appear to have some wear material on it that, in my case I suspect may be worn since it has obviously been slipping a lot as a result of all the oil inside of there. I'm wondering how one tells when the magnet needs to be replaced? Anyone know?

If anyone has any other trailer brake tech to add tot his feel free. The purpose of this thread is to learn about a component that I don't think anyone ever really pays attention to. I haven't seen any threads about it at least ...

al1tonyota · May 24, 2015

I'm not sure there is a replacement wear point on the magnet? I remodeled a 20' utility gooseneck for my dad several years back that was my first experience with electric brakes I replaced all four of the magnets because the brakes didn't work well and stopped uneven. When I got all of them pulled apart the old magnets were worn maybe 1/8" thinner than the new ones? The small spring on the back of the magnet was rusted and weak on a both axles on one side? If the spring is to weak it won't hold the magnet to the drum/armature. All of the shoes were thin but after seeing new ones they start out pretty thin! I adjusted all of them until they where dragging fairly hard. They seemed to work pretty well afterwards

tallnate · May 26, 2015

Check the armature surface area of the brake drum for wear. When I changed the brakes on my work trailer, the magnets were in bad shape and they had worn grooves into the surface of the drum where they ride. So I had to put new drums on the trailer as well as new magnets and brake pad assemblies.

Chuck19 · May 26, 2015

Www.nueratrailerparts.com
If they don't have it you don't need it !

Toddy · May 27, 2015

If I remember correctly it was just about same price to buy new backing plates with everything on them as it was to just replace parts. 4 bolts and brakes are done. Been awhile but an option to look at.

mac5005 · May 27, 2015

It was cheaper to buy new drums/hubs with bearings and seals, than it was to source new bearings and seals individually. The case was the same for the magnet assembly and shoes. I got new backing plates with shoes, magnets and all, already all assembled for less than shoes and a magnet kit.

This was on both 7k axles and my smaller 3500lb axles. Also allowed me to put brakes on both axles.

I get all my parts from agrisupply.

http://www.agrisupply.com/m/default.aspx

I'm following this thread as i am curious about the voltage drop causing a different in braking from left to right.

My left side locks up slightly sooner than the right. Bearings were all just cleaned and repacked, and new seals.

Meticulously adjusted the shoes to drag slightly.

Curious if the extra 7' of wire going to the right side brakes versus the left is enough to cause enough voltage drop to notice a difference.

My wiring runs runs down the drive side of trail, branches out for the brakes on the driver side, then turns and runs over to the pass side.

al1tonyota · May 27, 2015

mac5005 said:
It was cheaper to buy new drums/hubs with bearings and seals, than it was to source new bearings and seals individually. The case was the same for the magnet assembly and shoes. I got new backing plates with shoes, magnets and all, already all assembled for less than shoes and a magnet kit.

This was on both 7k axles and my smaller 3500lb axles. Also allowed me to put brakes on both axles.

I get all my parts from agrisupply.

http://www.agrisupply.com/m/default.aspx

I'm following this thread as i am curious about the voltage drop causing a different in braking from left to right.

My left side locks up slightly sooner than the right. Bearings were all just cleaned and repacked, and new seals.

Meticulously adjusted the shoes to drag slightly.

Curious if the extra 7' of wire going to the right side brakes versus the left is enough to cause enough voltage drop to notice a difference.

My wiring runs runs down the drive side of trail, branches out for the brakes on the driver side, then turns and runs over to the pass side.

Just curious you did keep the assyblies separate and use the correct ones left to right? There isn't enough voltage drop in that short of a distance to make a difference.

mac5005 · May 27, 2015

al1tonyota said:
Just curious you did keep the assyblies separate and use the correct ones left to right? There isn't enough voltage drop in that short of a distance to make a difference.

Yes the one pair I reused, kept the drum matched to the magnet, just repacked the bearings and new seals.

the new pair are assembled correctly an are correct for the side.

So yes. The lefts are on left and rights are on right. If I remember correctly, when assembled correctly the arm for the magnet is in front of the spindle, and when the brakes activated when moving forward is pulled in tension.

Went out and put some miles on it, wore off the high spots on the shoes/drum, and to bed the shoes in.

Still locks up in the same order by shortest distance of wire.

12 ga stranded wire with all soldered and heat shrink connections.

Sorry for the hijack.