Trailer tires are smoking when braking hard and trailer is empty....

Automatic slack adjuster, usually will have a adjustment plate on the side of the slack adjuster that is bolted onto the diff or axle beam . A manual slack adjuster will not have the adjustment plate that bolt on to the diff casing or the axle beam in case of a trailer.
Sometimes you will see an adjustment pin, like with some American truck then its a little pin on the front or rear of the slack adjuster that is also connected to the clevis or booster yoke. (sorry the parts are called differently in diff areas of the world.

Depending on the time you have I usually check if the travel of the springbrake yoke when applying the brakes , if it is more then 2" or 50mm I will check the adjustment. look at left and right operation , it should be insync ,if not, adjust brakes and check again. Also when the brakes are unapplied, pull the slack adjuster with your hand to simulate braking, it should be able to move about an inch or so, depending on the size of your biseps (lol) and return to the unbraked position instantaneously when you let it go. then it should be correct. Make sure the cam bushes are nor worn . make sure the linings are still good by checking , some lining will have wear indicators on them. Also check the response on the brake system when applying the foot or hand brake. It should activate very fast (split second) - nb! listen and observe , 1) listen to air releasing it should be quick like 1 second or less. then look at the slacks retracting it should have an immediate movement and then a secondary and it will move back to the unbrake position in about 2-4 seconds .

 

LOL why dont you just say I dont do the brake check when I do my pre/post trip and I have one side that is locking up. Could be one side is worn more, one side has contamination on the drum, grease, oil ect, one side may be set up more than the other. Silly thing is you wont know until you get under there and look.

 

The cause of the problem that you have might could be a few things. But trought elimination you can easily find the problem.
1) check the operating speed , when you tramp the brake pedal the brakes should activate in half a second. when you release the brake it you should hear an immediate air release (on the trailer) and slacks should return to the unbraked position within 3 to 4 seconds. is the brake shoes still okay or worn?
when this check okay go to next step.
2)check if the trailer is fitted with a load sensing valve. it should be fitted on the inside chassis above the axles with an load arm connected to one or two axles (for mechanical suspensions) if air suspension the load sensing valve will have two 8mm pipes coming from the air bellows to the valve.
it might be that the load sensing valve arm is not connected to the axle , I found in some cases when the arms break the truckers just tie it into a "lock " position. then the truck brakes don't vary between unladen and laden position.
3) it might be that a load sensing was previously replaced, to make sure if it was installed correctly, move the arm, going down to the axle, upward while applying the foot brake. if you see the brakes pushing a little harder the valve is setup correctly, if you hear air releasing the valve is wrong way around .
4)on the side of the trailer you should have a data plate that give you the load sensing valve installment lengths on the operating arms.

if you still have troubles use petrol and matches. lol just joking. feel free to ask if you struggle.

 

The "load sensing valve" has nothing to do with brake application, it only regulates ride height.

 

Good day Hammer,

Almost correct, but make sure as the descriptions are very close and sometimes confusing.

"Leveling valves" regulates the ride height on trailers or trucks fitted with an air suspension .

"load sensing valve or/and Relay load sensing valves" regulate air pressure to the spring brakes thus increasing or decreasing brake capacity.

Air suspension "load sensing valve or relay load sensing valves" is triggered with the air pressure differences from the " leveling valve " to increase or decrease air pressure to the springbrakes of the vehicle.

 

Yes sir, my apologies, as I misread the initial post. I will say I've never seen such a thing on any class 8 I've ever been around. In pre-ABS days they were on most of the smaller hydraulically-braked trucks, but I haven't been around those since the advent of ABS to know if they even install them nowadays.

The dinosaurs among us will remember the air valve on the dash to limit the front brakes when needed. And yeah, if you remember, you're an old #######!

 

lol! some things in life was much better in the olden days. unfortunately they improved the trucks but I cant say that about the new young drivers. I have a few trucks of my own. older models from 80's to late 90's . I only employ older drivers 50+ because they can still drive the old trucks and much better the old trucks than the young drivers the new trucks. I pay tribute to you Hammer, you guys rock! dinos rock! lol have a great day.