What Gauge Wiring For Installing Brake and 12V Circuits on Long Bus Towing A Trailer

Updated 09/26/2025 | Published 05/04/2025

Products Featured in This Question

Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires

(3535)

$118.67

10 Gauge Wire - Blue Primary - Per Foot

(109)

$1.61

Question:

I am currently converting a 4 way to a RV 7 way behind a 60’ bus. What size wires would I need to run from the brake controller to the 7 way connector for the trailer brakes and 12v power? It would need to accommodate voltage . The trailer would be a tandem axle 10k trailer. I believe the brakes would max at around 16 amps total at 12v. At that length I figure a 2 gauge wire, which seems overkill. Thanks for your help.

asked by: Ryan

Expert Reply:

Hey Ryan!

This is a good question. Even with a long bus like what you have though, 2 gauge wire is definitely going to be overkill for those brake output and 12V circuits. Going with 10 gauge wire like # 10-1-1 for both will be thick enough to prevent any significant voltage drop along the way and it's what I recommend going with. It's gonna be a lot cheaper too...

What kind of bus do you have? I assume it's an awesome conversion?

expert reply by: Chris R

Chris R.

9/26/2025

Hey Ryan, Did you end up using the 10 gauge wire for your setup? I'd love to hear how it worked out for your bus conversion, as it could help others with similar projects.