DIY Parking Brake Lock for Air Brakes

My RV is equipped with air brakes. One of the differences between air brakes and hydraulic automotive brakes is how the parking brake is actuated. Most cars have a lever in the passenger compartment attached to a cable that attaches to the rear brakes. Air brake systems use air (or the lack of it) to set the parking brake.

The parking brake on my RV is a yellow, square-shaped knob that you pull to engage. The travel (length of pull) is about a 1/4 of an inch. There’s a positive click when the brake engages.

I have two problems with this setup.

  1. It’s difficult to tell if the parking brake in engaged just by looking at it. The set and release positions appear identical.
  2. It’s easy to bump the knob and disengage the parking brake.

Unlike automobiles, there is no “Park” position on the transmission. The only thing keeping the RV from rolling away is the parking brake. A few times in parking lots I have shut off the engine and didn’t immediately set the parking brake. It’s a scary feeling when the RV starts to roll.

There are aftermarket solutions. Most involve a machined piece of metal block that is placed over the knob to restrict travel. Unfortunately, they are expensive running upwards of $100. I decided I could make one out of wood. Note: if you have a 3D printer you can download plans for one here.

It’s nothing special, just the end of a 2x4 shaped to fit behind the knob and restrict travel. It also serves as a visual indicator that the brake is set. I used a bandsaw and a chisel to form it. It took all of twenty minutes and two attempts to get the right shape and thickness.

I later painted it orange. Looks a little better and is easier to see when mounted.

painted orange

Written on July 4, 2018