Trailer brakes lock up

[Todd B]

When I leave my semi sit for a month or so the trailer brakes will lock on.  I can build my air to 120 lbs and they are locked up.  I keep moving my cliff hanger valve and after several tries it frees up.  Once free it works perfectly.  It seems this all started a couple of years ago when a mechanic adjusted my trailer brakes.  Any help??

[Plymouthy Adams]

are they so close that when sitting and the damp air that causes the drum surface to rust is so close to the shoe it makes a bonding action...have seen this with cars..even late model with discs can and will do this in a high moisture area..back them off or a more frequent cycling of the brakes may be short term cure till wear is such to alleviate the problem

[Todd B]

I thought about backing them off, I used to be able to slightly put my trailer brakes on as I run down through the gears, now the brakes are either off or completely on.  I have a hard time with it the way it is.  I thought they would wear faster then they are.  My trailer was an old military trailer and the brakes were the original shoes and in almost brand new condition.  I am not sure how to adjust them but I think there is an external threaded rod you adjust with lock nuts.

 

Thanks for the input

[NiftyFifty]

I wonder if it's the shoes, or the brake pot itself?

[MBF]

When I was driving for a living I adjusted the trailers (with the brakes off) by turning the adjustment on the arms until the brakeshoe was touching the drum and then backed off 3 clicks.  The rear of the tractor I did the same, but backed them off 6 clicks.   That way the trailer brakes were always the first engaged when using the brake pedal.  Have you greased the linkage, and are these the old S cam design?   If you're in a damp climate or an area where it goes below freezing at night it might just be condensation rusting the drums to the shoes.  If its going to sit for a long time (and if you don't have maxi cans on the trailer) you may want to bleed down the trailer air tank, and just chock the wheels.   I think the next time I drove it I'd drag the brakes for awhile on the trailer to wear off any rust and boil out any accumulated moisture.  You also may want to give your air system a shot of airbrake antifreeze to help get rid of any moisture in the system.   Mike

[52b3b Joe]

Typically like Mike said, adjust them in until they are touching the drum, then back them off a 1/4 turn. I too normally adjust them to engage slightly faster on the rear of the vehicle. I've only adjusted modern trucks and trailers, so I'm not sure how your trailer is set-up. There are two styles I know of. The first is the button style where you have to use a screw drive (they do make a tool for it though) to pull the a button out and then turn the adjusting nut. The second style is the ratcheting style. The ratcheting ones can sometimes be touch to turn. If they are the ratcheting style, make sure they are clicking as you adjust them. If they don't "click", then they are normally bad. Also make sure everything for the brakes are greased so they are working smoothly. I don't know how your trailer is set-up, but hopefully this helps!