Parts Needed to Add Electric Drum Brakes to a Trailer

idler hubTrailer hub-and-drum

Whether you are adding electric drum brakes to a trailer without any existing brakes or changing from hydraulic to electric brakes, you will need some basic information to build a system that will stop your trailer safely and dependably. The following article and tables provide information about your options and will help you find parts that will work together. If you just want to find parts quickly, see our Parts Reference Table, below.





Parts Reference Table


Parts for Adding
Electric Drum Trailer Brakes
TrailerTruck
PartBrake Mounting FlangeSpindleBrake AssemblyHub-and-Drum Trailer WiringBreakaway KitBrake Controller
Brake Mounting Flange Spindle diagram Electric Drum Brake Assembly Straight on View of Hub Accessories for wiring a trailer for electric brakes Breakaway kit Electric Brake Controller
ConsiderAxle diameterBearing and seal dimensions
B -
C -
D -
Axle capacity -
Brake assembly diameter

Brake shoe width
Hub diameter

Hub bolt pattern
Trailer connector must match connector on vehicle Number of axles on trailer Vehicle-specific wiring may be available




Trailer Brake Mounting Flanges


To operate the brakes, your trailer's axle must have a brake mounting flange attached behind the existing hub assembly on each side. Most axles have these, but if yours has no brake mounting flanges, you have two options:


1. You can replace the axle with a properly rated one that already has brake flanges welded in place. Ordering a new axle complete with electric brake assemblies and drums may actually cost less than buying separate parts. However, to order a complete axle you will need to know the axle capacity, wheel bolt pattern, spindle type (whether it is drop or straight) and type of brake assembly - in this case, electric. You will also need to know the distance between your trailer's springs, center to center, and between the hub faces.


brake mounting flange

2. You can purchase brake flanges and have a qualified welder weld them to the axle. When a brake mounting flange is welded to an axle, it must be welded square and concentric. This usually requires a jig to hold both parts in position. A trailer shop should have the equipment and personnel to weld brake mounting flanges to your axle.


This is the most popular brake mounting flange. It's a square, 4-bolt pattern that is used on most axles up to and including 3,500 lbs. The next-most-popular flange is the 5-bolt design, which is commonly used on 5,200-lb, 6,000-lb and 7,000-lb axles. The pattern of the holes in the flange is standard, so all you need to note is the number of holes in the mounting flange, and the axle diameter.





Trailer Hub-and-Drum Assemblies


Trailer spindle diagram

If your trailer axle has brake flanges and you plan to add the other brake components separately, you must select hub-and-drum assemblies that are compatible with the trailer spindles. The numbers stamped into your trailer's existing bearings and seals will help you determine the proper hub-and-drum assemblies. You will also need to know the wheel bolt pattern of your existing hubs so that the new hubs will match up with your existing wheels. If you cannot find part numbers for the bearings and seals, you can measure the spindles at the inner (C in diagram) and outer (D in diagram) bearing surfaces as well as the seal contact surfaces (B in diagram).



Trailer hub-and-drumspindle

This is our most popular setup for a 3,500-lb axle. Notice the tapered spindle. It uses L68149 inner bearings (dimension C) and L44649 outer bearings (dimension D). The 10" hub-and-drum with a 5 on 4-1/2" wheel bolt pattern is also pictured.






Trailer Brake Assemblies


Once you've selected a hub-and-drum assembly, you can choose a compatible brake assembly. You need to know that the brake assembly is compatible with the brake mounting flange and with the drum's diameter and depth.



Brake Assembly Drum with diameter and depth indicated

The labeled drum shows the measurements you need to know to select a brake assembly. For the 3,500-lb axle, the 10" brake assembly is shown. Only one size is available for a 10" hub-and-drum assembly. You'll just need to choose between self-adjusting and manual-adjust brakes.





Wiring a Trailer for Electric Brakes


Parts needed to add wiring to trailer for electric brakes

You will need to run wiring from the front of your trailer to your trailer brakes to carry electric power to them. In addition to wire, you may need connectors, zip-ties, wire clips, electrical tape, and ground screws. You'll also have to convert your trailer connector to a 7-way that includes a circuit for electric brakes.


Each brake assembly should have 2 wires coming out of the back. Attach one of these wires to the trailer for the ground. The other wire will receive power. It doesn't matter which wire you use for which purpose.



Diagram of power wire going to each trailer brake

Run a 10-gauge wire (which will have blue insulation) from the front of the trailer to one of the trailer brakes. This will be your power wire. Connect the power wire to the non-grounded wire on one of the brakes, then run another wire from the power wire on this brake to the brake on the other side of the axle. If you have more than 2 brakes, run power to all of them in the same way.


If possible run the wire through openings in the frame. You can also use hangers and zip-ties to route the wire. You want the wire to be close to the bottom of the trailer and not hanging down where it could get snagged or damaged.


You can use butt and quick-splice connectors to connect the wires. To help keep water out of your wiring connections, wrap them with electrical tape.


You will need to replace the 4-way connector at the front of your trailer with a 7-way that includes a connection to carry power to the brakes.





Electric Trailer Brake Controllers and Wiring


brake controller etbc7 brake wiring kit

Finally, to operate your electric brakes, you will need to set up your tow vehicle with a brake controller and the proper wiring. Our article, Trailer Brake Controller Information, explains brake controller similarities and differences, and our Brake Controller Application Guide will help you to determine all the parts needed for your vehicle.



Breakaway Kits

Breakaway kit

Breakaway kits apply the trailer's brakes if the trailer becomes uncoupled from the tow vehicle. These systems include a battery and wiring, and sometimes have a built-in charger. When choosing a breakaway kit, be sure that it is recommended for use with the number of axles that have brakes on your trailer.





Common Combinations of Trailer Brake Components


Note: The following table shows common combinations of trailer components. Some trailers may have other combinations of components, so you should always verify fit before ordering replacement parts.


Typical Components by Axle Capacity for Adding Electric Drum Brakes
Axle Size EZ Lube Option Brake Flange Bearings Seal Brake Assembly Hub/Drum and
Bolt Pattern
Breakaway Kit
2,000-lb Axle

1-3/4" Diameter
Standard 4-34 Inner - L44649
Outer - L44649
10-9LH - 7" x 1-1/4"
RH - 7" x 1-1/4"
4 on 4" - 8-173-16UC3
5 on 4-1/2" - 8-257-5UC3
50-80-313
EZ Lube 4-34 Inner - L44649
Outer - L44649
RG06-020 (10-60)LH - 7" x 1-1/4"
RH - 7" x 1-1/4"
4 on 4" - 8-173-16UC3-EZ
5 on 4-1/2" - 8-257-5UC3-EZ
50-80-313
3,500-lb Axle

2-3/8" Diameter
Standard4-35Inner - L68149
Outer - L44649
58846LH - 10" x 2-1/4"
RH - 10" x 2-1/4"
5 on 4-1/2" - AKHD-545-35-K50-80-313
EZ Lube4-35Inner - L68149
Outer - L44649
10-19LH - 10" x 2-1/4"
RH - 10" x 2-1/4"
5 on 4-1/2" - AKHD-545-35-EZ-K50-80-313
5,200-lb and
6,000-lb Axle

3" Diameter
Standard4-44-1Inner - 25580
Outer -
15123 or
LM67048
GS-2125DL (10-1)
or
GS-2250DL
LH - 12" x 2"
RH - 12" x 2"
6 on 5-1/2" - AKHD-655-6-K50-80-313
Inner - 25580
Outer -
02475 or
14125A
GS-2125DL (10-1)
or
GS-2250DL
LH - 12" x 2"
RH - 12" x 2"
8 on 6-1/2" - AKHD-865-7-2-K50-80-313
EZ Lube4-44-1Inner - 25580
Outer -
15123 or
LM67048
RG06-090 (10-10)
or
RG06-070 (10-36)
LH - 12" x 2"
RH - 12" x 2"
6 on 5-1/2" - 8-201-5UC3-EZ50-80-313
Inner - 25580
Outer -
02475 or
14125A
RG06-090 (10-10)
or
RG06-070 (10-36)
LH - 12" x 2"
RH - 12" x 2"
8 on 6-1/2" - AKHD-865-7-2-EZ50-80-313

Updated by: Raymond P.

Last updated: 7/3/18





Questions and Comments about this Article

Jeff P.

I have a 2005 Triton ATV128 trailer with 20.5x8.0-10 tires and I’d like to add electric brakes to it. It has the 4-bolt brake flange on each end of the Reliable axle. Can you help me figure out which brake kit to purchase?

Etrailer Expert
Reply from Jon G.

You should be able to use the 7" brakes like what you find in the kit # AKEBRK-2 . Attached is our selection of hub and drum assemblies that you can filter through as well. You'll want to match the bearing and grease seal dimensions with what your current hubs have.

Michael S.

I have been renovating a 29' 1976 Airstream. It has two 4000# axles and 12? drums. I think the axles were produced by Henchen but they are no longer in business. Two years ago we were traveling through Las Vegas. While there, I took the trailer to a shop and had them put new brake assemblies (including hubs and drums) on both axles. This weekend I wanted to pack the bearings. When I pulled the hubs and drums off of the back axle, I saw that the front shoes on both ends looked like they were new. The rear shoes are paper thin. I have no clue why they are worn this way. At the very least I need new shoes. The rest of the components look almost new. I looked through the etrailer site but could not find the brake shoes I need for my 12" drums. Can you tell me what brake shoes on your web page I can use to rebuild my brakes? Thanks,

Etrailer Expert
Reply from Jon G.

We normally just recommend picking up a completely new brake assembly set so that you know everything else is worn just as much as the brakes. Do you know what brand brake assemblies were installed? If you're only wanting the brake pads then we need to make sure that you're using the correct replacements. What I'm guessing is that either your front brakes aren't getting power or your rear brakes were adjusted way too aggressively and were doing all of the stopping for your trailer.

Reply from Michael S.

@JonG Thank you for getting back to me. I got the brake assemblies on the rear axle from the shop that mounted the new backing plates. Not sure what the brand is but I will be pulling the hubs/drums/ and looking for identifiers. Reason I had the brakes worked on was that the components of each hub/drum/wheel were heating up and I could not find out why. Not long after I had the brakes rebuilt I read an article about controllers gone bad. Since I replaced the controller the wheel/hub assemblies are no longer heating up. I thought that the problem was solved until I pulled off the two hubs and drums and saw the peculiar wear on the rear shoes. I want to rebuild the brakes but I don't know which seal I need or which backing plate assembly will work for this axle.

Etrailer Expert
Reply from Jon G.

@MichaelS If the brake controller was the problem then I don't see why it would only be affecting 1 set of brakes. I think it has to do with the installation and how the wiring is connected.

Reply from Michael S.

@JonG Hi Jon, When I get on the ground and have the hub/drums off I will check the wiring and make corrections. I have to replace the rear backing plate but before I start pulling hubs and drums off I need to purchase the backing plate assembly and seals to have on hand. Will any of the 12" backing plate assemblies work? I was told that the axles are 4000# each. Does it matter if I put the backing plate assemblies that are rated at 5000# on my axles? From what I can tell the 5000# assembly fits onto the 6 lug hub and 5 bolt flange that I have. I would like to have the seals on hand when I pull the hub/drum off. Which seals do I need?

Etrailer Expert
Reply from Jon G.

@MichaelS If you are needing to replace just the backing plates then you need to get an exact replacement. If you plan on changing out your whole brake assembly then you should be able to just use a 12" setup like the kit # 23-458-459 . Keep in mind that whatever you do to one side of the axle you'll need to do to the other side. I would need you to measure your spindle so I know what hub/drum assembly will fit. I've attached a link to one of our expert pages that you can reference for where to measure on your spindle.

Hugh P.

Hi, I want to add electric brakes to my Ubuilt trailer. Presently it does not have brakes. The spindles are 70's Rambler with a 4x 3.5" mounting flange. I see that the standard is 4x4" flange. Is there any electric brake backing plate that has this Rambler bolt pattern. Or would it be possible to find backing plates that have not been drilled? The drums are 10" x 2.25". Thanks for any assistance,

Etrailer Expert
Reply from Jon G.

When you mention 4" x 3.5" mounting flange are you talking about the size of the flange itself, or the size of the bolt pattern?

Reply from Hugh P.

Hi Jon, this is the bolt pattern on the mounting flange (4x3.5") that is on the trailer. Cheers,

Etrailer Expert
Reply from Jon G.

@HughP It doesn't look like any of our brake mounting flanges have that same bolt pattern. There might be something out there but if your trailer is from the 70's you're probably going to have a hard time finding something that matches. You would either need to have a professional welder cut off your current flange and weld on a new one, or you'll need to swap out your axle for a newer one with a standard brake mounting flange bolt pattern. If it's the original axle that came on your trailer I would encourage you to look into a new axle over swapping out the brake mounting flange. Here is a link to our selection of axles that you can check out if you would like to go that direction.

Neil

I have a classic 2006 aliner camper that weighs 2000 lbs. It does not have brakes. I pull it with my Jeep grand cherokee and feel I need better control stopping it. I has the square flange to bolt up the drum. Exactly what parts do I need? Thanks

Etrailer Expert
Reply from Jon G.

You should be able to use the brake kit # K23-103-104-00 which has the 4" x 4" mounting flange bolt pattern and then one of the hub and drum assemblies from the linked selection. You'll need to make sure the bearings from your current setup match with the hub and drum assembly prior to ordering. Aside from that you need a junction box # e99011 , 10 gauge wiring # 10-1-1 to reach from the junction box to the brakes, and a breakaway battery kit like part # 20400 . If you don't already have a brake controller in your Jeep let me know and I can help you figure that part out too.

Reply from Neil

@JonG thanks Jon I’ll be getting back with you again

Reply from Neil

@JonG What is included with the kit# K23-103-104-00

Etrailer Expert
Reply from Jon G.

@Neil The 2 brake assemblies, 4 rubber plugs, and 8 nuts for installing the assemblies.

Scott R.

Is the breakaway kit required?

Etrailer Expert
Reply from Jon G.

If you have trailer brakes then yes, a breakaway kit is required by law.

Paul Q.

This article was very informative. But I'm I just purchased an older 1959 Shasta camper. It seams to have a braking system, but the wires going to the wheels are disconnected and not being used. I'm wondering if the brakes on the hubs are not working or can they be repaired or should a replacement be in order??? Thanks for any suggestions.

Etrailer Expert
Reply from Jon G.

I would honestly just replace them. It sounds like someone didn't want to use the brakes so they disconnected the wiring and just drove without them. If that was a while ago then the brakes are probably in bad shape and it would be much more safe to replace them.



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