Weak trailer brakes. Sure could use some ideas here!

[Cord]

I have a 32' flat bed tri-axle gooseneck trailer. The trailer has electric brakes on each axle. When I first got the trailer, I found the shoes to be wiped out. Some brakes obviously hadn't worked for some time, others where grinding on metal. I went with new backing plates, magnets, and shoes. The brakes are the self-adjusting type. I had the drums turned but was disappointed when I found they were all cut oversized. I assembled the brakes and adjusted them so they were lightly dragging. I packed the bearings and then filled the hubs with high-temp grease using the bearing buddy caps.

When I went to burnish the brakes I found there was only one that was working. I reached out to Dexter who said the wiring was undersized. Strange because this was the factory wiring. I ran a new 10g wire, both power and a dedicated ground back to the brakes. No change in effectiveness.

I used the trailer for a while like this and then I took it to a dealer for him to diagnose. He said there was "some" grease on the shoes which he cleaned, but otherwise everything looked good. He didn't know why they were not effective.

After thinking about this for a while, it occurred to me the problem might be the oversized drums. I bought new drums and when I went to install them, I found the seals had blown soaking the shoes in grease. It was obvious the brakes got warm at some point and the over-filled hubs became pressurized pushing the grease out. I ditched the bearing buddies and repacked the bearings in a more traditional manner. I washed the shoes until the rag was clean. When I assembled the brakes, I found that the brakes were slightly more effective. Now one brake will lock, but the others are just putting in a modest effort; but they are working.

In spring I'll have a heavy load to haul over a long distance so I really need these brakes to work. I'm hoping you guys might have some ideas as to what I can check next. I seem to recall having tested them with the jump pack, but I don't remember what the outcome of that test was. I certainly can repeat it and post the results.

The tow vehicle is a 2015 GMC 2500. I don't believe the problem is with the truck because I have other electric trailers and they brake OK.

 

[D&D]

3 things I would check
1) all trailer grounds plus truck to trailer ground
2) how the trailer was rewired, connection points all good? Series or Parallel paths?
3) current output on brake controller

 

[MTGreen]

I'm assuming you have a modern inertial adjustable brake controller like a Tekonsha T3 or equivalent .
I would test the voltage that's actually getting to the magnets. Maybe get someone to hold the manual trailer brake actuator in the cab and use a voltmeter as close to the magnets as possible. If you're not getting 12v to the magnets at full actuation with your brake controller adjusted to max output you're not getting full braking output

Also D&D above makes an excellent point about serial vs parallel connections for your axles. If you're wired in series you're only getting meaningful output to your first axle

 

[gstrom99]

I'd suspect the connector/ground or the controller. Is the controller built into the truck (OEM) and/or adjustable?

 

[Snobdds]

Grounds. Check with a power probe your getting an actual ground at your grounds.

 

[mrmikey]

Make sure you put the shoes on the correct position, front to rear, primary /secondary as the primary shoe is what actuates the secondary shoe. Sounds to me like an electrical problem as was said, either truck or trailer wired incorrectly.

 

[oliver1555]

Check to see what the amperage draw is on each magnet. It should be 2.5 - 3 amps at full actuation, depending on brake size. Just because you have voltage, it does not mean there is enough amperage for the brakes to properly work (bad connections, insufficient wire size, poor grounds, etc.). Here is a link to Dexter's troubleshooting page.
Home | Dexter Axle Co

 

[mjonesnh]

Experienced similar reduced braking on my tandem axle trailer. Like you I installed new backing plates assy, with new shoes and magnets. Not much difference. Then added several new ground connections at various locations on trailer. That helped noticeably. Next I turned up the voltage of the P3 controller to 8.1 from 6.8. Now everything seems back to normal. Not sure why all of sudden the P3 wanted more voltage than previous but increasing it to 8.1 made substantial difference

 

[Too many Kubotas]

There's no practical way to clean grease off of brake shoes or pads. Definitely not with with rags anyway.

Once oily or greasy they're junk. Drums and rotors are easily degreased with brake cleaner, though.

Either way, not relying on Bearing Buddys for getting grease to the bearings is a good idea.

 

[jaxs]

I believe all the bases have been covered but the bases are often evasive when it comes to trailer wiring. Since faulty ground accounts for most trailer light and brake problems let's solve that once and for all. Braze a 1/4" brass bolt head to trailer frame and connect ground from 7 way to it with brass washers and nut. If brake magnet grounds connect to backing plates ,extend wires to additional brass bolts brazed to frame. Reason for doing this is there are several BOLTED TOGEATHER components where high resistance can set up. Examine frame to make certain there is a continus path through WELDED joints going back to 7 way ground bolt. If lo and behold frame is bolted together, braze bolts on either sides of joint and jumper with copper wire or braze copper plumber strap across joint. While you have tools out, add bolts for light grounds. This pretty much takes ground failures out of the equation for life of trailer. Test brakes. If no joy go to work on hot wire connections starting at and including 7 way. There are no better cleaners and protectants than the Deoxit line of products. If brakes still don't work you have at least set the trailer up for reliable testing and long term dependabe wiring.