Brake Wire

When we had our 22' fifth wheel, the passenger front tire would always lock up but the others kept rolling... the problem wasn't necessarily the wire size, but how it was wired. The factory routed the wires along the right side of the trailer, then tapped off and ran across to the left side. The right front tire was first in the circuit.

I rebuilt the wiring using a variety of sizes. As Larry Cad stated, each brake pulls around 3 amps at full braking. 3 amps is easily carried by 16 gauge, which is the same size as provided on the brake puck. I wired each of the 4 brakes to an equal length 16 gauge pigtail. At the center of each axle, I joined the pigtails to equal lengths of 14 gauge, then ran those back to the right frame rail. Those, then were joined to a 12 gauge lead that ran to the 7 pin plug.
All connections were soldered, sealed with liquid tape, then protected with heat shrink.

The point of this exercise was to provide equal current and voltage to each brake. From that point forward, I never slid one wheel, but could lock all four up if desired. It was a vastly different towing experience.

All that said, the point isn't necessarily just the wire size, but how its wired. You don't need 10 or 8 gauge wire to each brake, that's overkill. But you do need to consider both the total current on each lead and how it's balanced.

On the tow vehicle, you'll need an adequate size wire for the job. At 12-14 amps maximum for 4 brake trailers, 12 gauge (20 amp max) is all that is needed. In practice, you'll never pull 12-14 amps on a constant basis. I'd venture a guess that current during usual braking is commonly between 1 and, say 6 amps. Those who have current readouts on their brake controllers know the story.

Sjm9911 wrote:
I will be the on the oposote side. Etrailor recomended 10/2 wire. Way to big and cumbersome to attache to the way smaller wires in the electric brakes. If i had to do it over 16 guage would be enough. I think my original stuff was that big or smaller.

And this is why I compare getting information from a forum the equivalent of asking the folks sitting along the campground bar what they think. Same odds of wrong or right answers

"I'm no expert but I play one online"

Safe travels

Sjm9911 wrote:
I will be the on the oposote side. Etrailor recomended 10/2 wire. Way to big and cumbersome to attache to the way smaller wires in the electric brakes. If i had to do it over 16 guage would be enough. I think my original stuff was that big or smaller.

You cannot use a wire size that is the same as the wire size on the brakes. The trailer wire has to carry enough current (amps) to power all the brakes, not just one. Two trailer wheels takes less amps than a 4 wheel trailer. 6 wheel trailer takes more amps than a 4 wheel, and so on.

Most trailer wire harnesses use #10 wire which is rated at 30 amps.

On each individual electric brake magnet the amperage draw would be 3.0 to 3.2 max amps at 12 to 13 volts on 7-inch brake magnets and 3.2 to 4.0 max amps at 12 to 13 volts on 10 and 12-inch brake magnets.

The max amperage draw for the brake magnets on a single axle trailer (2 brakes) would be 6.3 to 6.8 max amps on a 7-inch brake system and 7.5 to 8.2 max amps on 10 and 12-inch brake system. The amps will be higher if using a tandem axle or triple axle trailer.

10 or 12 is more than adequate. when taking into account the coil resistance of each brake magnet and typical runs, drop is acceptable. with the factory skimpy wiring on our and a prodigy, full brake on the prodigy wouldn't lock up the brakes on dry pavement. After going to 12g and soldering the connections, including bypassing the typical side to side wiring in the axle, 6 or 7 will lock up the brakes at 60mph on dry pavement.

I get the principles and practices, i just figured the manafature has allready considered the drop into the specs. So its designed to work woth the guage it has and to upgrade it will not nessassarly equate better stopping.

Sjm9911 wrote:
I will be the on the oposote side. Etrailor recomended 10/2 wire. Way to big and cumbersome to attache to the way smaller wires in the electric brakes. If i had to do it over 16 guage would be enough. I think my original stuff was that big or smaller.

That would be OK if you don't mind having as much as 30% less breaking capacity available.

The smaller size of wire, the higher the resistance, that resistance eats up valuable voltage, less voltage equals less current running through the magnets, less current running though the magnets equals less strength of the magnets which means the brake shoes have less gripping power on the drum..

Moving to 10 ga wire from factory 14 ga wire can gain about 20% more braking power available.

As far as dealing with thicker wire, yeah, can be a pain, but once again, there are ways around that issue. You can use what is called extra flex wire, it uses very fine strands of wire which makes for a much easier to flex wire.

Myself, I used two pairs of 10 ga wire from front of trailer to the axles.. More brakes than I need and do not have to set my controller above 5.5 out of 10 on the output.

No less than 12 AWG. The more copper strands in the wire the better.

I would recommend this wire.
Brake wire

I will be the on the oposote side. Etrailor recomended 10/2 wire. Way to big and cumbersome to attache to the way smaller wires in the electric brakes. If i had to do it over 16 guage would be enough. I think my original stuff was that big or smaller.

The bigger the wire the less voltage drop you will have. Using 12g is fine. 10g is better. 8g is better still, and so on. Use the largest wire you can comfortably use. Second the suggestion to use only marine wire.

Personally, I wouldn't go smaller than 10g.