OT--Trailer Brakes

[David in TN]

I have a semi trailer that I use for storage and I want to move it forward a few feet. There are two air fittings on the front of it, one says service and I think the other says emergency, best I remember. I can get an air line to it from my shop compressor. If I tap into the service line and apply air will that release the brakes? It has only been here a month so they shouldn't be stuck. Haven't tried yet, but I'm hoping that I can move it with my tractor by picking up the front of the trailer with the loader and then slowly backing up I only need to go about 20 feet.

 

[Anonymous-0]

Apply air to the emergency hose. this is the supply for trailer. the service hose would apply brakes if released first with the emergency hose.

 

[Rexalot]

If you can't get air to it, you can manually release the brakes. On each brake there should be a plug that can be removed on the top of the cylinder that will let you screw in a threaded bolt to push the piston back effectively releasing the brake.

 

[DMont]

Each axle has 2 rods that actuate the brake shoes. The rods have bell cranks that are actuated by the air chambers. Each rod has a bolt at the bellcrank that will release the tension and allow the spring applied brakes to release. The bolt is a 9/16 wrench size usually. The air chambers have the springs inside that apply the brakes when the tractor is disconnected. Only problem here is that you will need to adjust the brakes once released by the bellcrank.

 

[Donnie Baker]

Put air to the one marked emergency it should be the one to the left (drivers side) and give it a few minutes to air up after a month there is a good chance the trailer has lost its air supply, I gotta go

 

[john in la]

The brakes are being held in PARK by springs. Apply air to the emergecy line (The RED one) and the brakes will release. It may take a few minuntes because you need to fill the tanks and let it build up to about 90 lbs of pressure before they will fully release.
You will need to keep this air hooked up during the entire move. If you take the hose loose the air will leak out applying the brakes again. This is why it is called the emergency line. It is a break away saftey brake.

 

[john in la]

The bolt is really a special T bolt. You must have the special bolt to release the brakes this way.
While each brake cylinder is sold with the bolt attached; they often fall off during normal driving because some fool in the past did not put them back correctly after using them.

 

[Doug N]

Yes, most below are right. It's called caging the brakes. It's a special T-looking bolt. Stick the T into the center hole in the back of the pancake chamber, give it a quarter turn and try to pull it out. If it won't come out, you are locked in and can start turning the nut in.

When you put it in, make sure the nut is backed all the way off to the end of the cage bolt. You will have to turn that nut d*mn near all the way to release the brakes.

You can air it up, but it will take alot longer to plug fittings on one side, and make adapters to hook air line up.
Doug N

 

[John M]

When I was contracting for the company I worked for before the job I have now, we had to repo a rental storage trailer, but the only thing that we had to get back where the storage trailer was was a small yard dog that had hydraulic brakes. The yard dog had been special ordered for one trailer we used on the yard.Anyways, we took a gas driven air compressor, attached a quick disconnect to the compressor, the other end to the trailer, ran the compressor, released the connection and the air stayed in the lines on the trailer long enough for us to pull the trailer out to be able to hook it to the truck. We had to reattach the glad hand hook up when we got the trailer out.

 

[Randy-IA]

And while the t-bolt idea can work it's not such a good idea depending on the condition of the air chambers . The spring pressure inside them is VERY high . The best way to do this is mentioned before , by airing the trailer up with your compressor , but don't go over 120 -130 psi . Otherwise chock the wheels and crawl under and look at the rod that comes out of the air chambers , follow it to the crank that moves the bar that goes into the brake , that crank is called a slack adjuster and looks like half a dogbone or a connecting rod in an engine , there should be a hex bolt sticking out the narrow side of the big end with a collar around it preventing you from putting a wrench on it . That collar is spring loaded to keep the hex bolt from turning so you need to push it back which sometimes requires a hammer and punch and some gentle hammering . If they are loose put the box end 9/16th's on it and watch the brake linings in the drum . Turn the bolt in whatever direction is needed to make the linings move away from the drums . It's really pretty easy once you look at it . If it's a newer trailer it might have self adjusters on it but they should work the same way . Good luck . BTW - The bolt might turn pretty hard . I'm assuming it's an older trailer since it's being used as a storage trailer but it still should work similar if it's a newer trailer ...Randy