How Do Hydraulic Drum Brakes Lock Up if Trailer Becomes Uncoupled From Tow Vehicle

Published 06/20/2018

Products Featured in This Question

etrailer Hydraulic Trailer Brakes - Uni-Servo - Dacromet - 10" - Left/Right - 3.5K

(166)

$170.14

Demco Hydraulic Brake Actuator - Drum - Zinc - 2" Ball - 7,000 lbs

(350)

$155.54

Question:

Hi, I would like to know if the Hydraulic Trailer Brake Kit locks up if it came unhitched? its to comply with Maryland safety law.

asked by: Jonnie

Expert Reply:

The etrailer.com Hydraulic Trailer Brake Kit # AKUBRK-35-D referenced in your question do not, by themselves, lock up if the trailer were to come unhitched. This is the case with any hydraulic brake assembly.

The mechanism that allows hydraulic brakes to lock up if the trailer were to ever come uncoupled with the tow vehicle is located on the surge actuator, such as with the Demco # DM72VR. This breakaway cable should be located on the top of your actuator (see attached image). You will attach the cable to your tow vehicle so that it will pull on the lever if the trailer comes uncoupled. This will actuate the master cylinder to apply pressure to the brakes and stop the trailer from a runaway situation.

I have attached a short video demonstration on this particular actuator that you can also check out.

expert reply by: Chris R