How to Pick Out Brakes for 3,500 lb Boat Trailer with Tandem Axles

Question:

Almost at the finish line. A few dumb questions and I should be good to order. Do I need a controller on the trailer or just what I install in the truck? Is there a special wiring/hardware kit to run electricity from the brakes to the controller, or to the back of the truck at the connection plug? I saw the hardware kit #BRKH12 but not sure what wiring is needed. Does this controller lock-out the back up brakes or is that a different controller? My truck is a 2004 GMC Envoy XL with the 4.2L engine. I have the common connector plug on the back of the truck for a 4-connection harness - for the brake lights as of now. What else am I missing?

asked by: Brad V

Helpful Expert Reply:

Installing brakes on a trailer really isn't too bad. The install is pretty basic and a DIYer like yourself wouldn't have a problem at all. To determine the parts you need though we need to for sure know what axles/spindles you have so that we pick out the right parts. I attached a couple guides for that down below for you to check out.

There are a lot of boat trailers that have great results with electric drum brakes so if that's a route you are interested in that's what I would recommend you go with.

expert reply by: Jameson C

click to enlarge

Brad V.

4/20/2018

I pulled off my trailer wheel and hacked off the rusty remains of the previous brakes, leaving me with the axle end plate (don't know the official name of it). The end plate is rusted but sturdy although I rounded the holes a bit. Is there a metal plate I can attach over the existing plate and then the big question is what do I need to purchase for my brakes? I'm still not sure if I should get electric or surge - it would depend on cost and needed DIY expertise. I guess I need a brake kit with brakes, lines and a new actuator that has the same 5 hole pattern. The inside of my wheel is 14", the boat is about 3200lbs (if that matters) and the trailer is tandem but I'm only planning to put brakes on the rear. I included 2 pictures of the end of the axle. Thanks for your assistance and please ask me anything if I missed it.

Jameson C.

4/20/2018

So what we need know is to know the dimensions of the spindle (that metal section that the hub was installed on) so that we can figure out which hub fits it. If you check out the picture I attached you'll see the three areas I need dimensions for. I need to know the seal, inner bearing, and outer bearing diameters.

Brad V.

4/24/2018

Jameson, Thanks for your assistance. Here are the measurements for the spindles and I'm counting on you to tell me all that I need for the electric brakes. I have a 12" drum on my wheels - they are rusty but fine. I have a 5 bolt pattern for the brake kit - I'm assuming it is a 5200lb axle. On the diagram you sent for measurements, A = 2 1/4, B = 2 1/4, C = 1/3/4, D = 1 3/8, E = 1, F= 2, Bearing ID = 1 3/8, Race OD = 2 1/8, Seal ID = 1, Seal OD = 1 3/4. I would also need the Inner bearing assembly - the current bearing has a OD = 3" and an ID = 2 1/4. I need the wiring (at least 20' to get to the front of the trailer) and the mounting bolts and hardware. I will also need whatever control box/actuator and whatever links it up to my truck. I have a very sturdy coupler from the old surge brakes. I hope I gave you enough to work with. Works some magic for me please. Thanks.

Jameson C.

4/24/2018

So based on the dimensions you listed you have a number 42 spindle which is very common. The trailer hub part # 42866UC3 will fit this easily and will work well for brake drums. For brake assemblies you'd then want the kit part # 23-458-459 which includes an assembly for both sides of the axle. For a brake controller I would recommend the Prodigy P3 Brake Controller part # 90195. This is our best selling brake controller because of how well it works and how easy it is to setup. This is a proportional brake controller that senses the amount of braking the tow vehicle is applying and applies a proportionate amount to the trailer brakes. This will be the last brake controller you buy. It can easily be transferred to future vehicles as well. I'd need to know what the year/make/model of your vehicle is to determine the best way to install the brake controller. Also what type of trailer wiring does it have at the rear of the truck?