brakes

[big truck driver]

do you adjust trailer brakes at the same time when you do the truck

[roadranger]

You "check" them, you don't "adjust" them - unless it is a very old trailer or tractor with manual adjusters. Automatic adjusters have been standard since 1990 or so? If an automatic adjuster is out-of-adjustment it needs to be rebuilt or replaced - "adjusting" it is just masking the real problem and it will probably be out again in a couple days (or hours!) ...

[CaptCaveman]

You can adjust automatic slack adjusters but its a pointless exercise unless the adjuster isn't working or DOT is running a safety blitz and you want to make sure your brakes are "snug".

[Kranky]

Where I work, whenever I have a truck in for PM, I'll manually adjust the brakes just to be sure that they're within spec.

And if I find one that is "way out" of adjustment, then the auto slack gets replaced.

[Mackmechanic]

Where I work, whenever I have a truck in for PM, I'll manually adjust the brakes just to be sure that they're within spec.

And if I find one that is "way out" of adjustment, then the auto slack gets replaced.

Exactly

We have to check and adjust the slacks, manual or not


Of course, the way vocational trucks run through brakes, it probably isnt a bad thing lol

[allan5oh]

I'll manually adjust the brakes just to be sure that they're within spec.

Checking and adjusting are two totally different things.

If you have automatic slacks, and you check them and they're not adjusting correctly, they get tossed.

You do NOT adjust auto slacks. If they're out of spec, there's something wrong with the system and they need to be REPLACED.

Not sure if this is correct but this is what I was told.

Get on a hill and roll backwards tapping the brakes to cause the trailer slack adjusters to adjust.

Step on the brake up to 90 psi application to cause the truck slack adjusters to adjust.

Is this correct?

[Kranky]

I'll manually adjust the brakes just to be sure that they're within spec.

Checking and adjusting are two totally different things.

If you have automatic slacks, and you check them and they're not adjusting correctly, they get tossed.

You do NOT adjust auto slacks. If they're out of spec, there's something wrong with the system and they need to be REPLACED.

Evidently you missed the second sentence in my post Allan:

And if I find one that is "way out" of adjustment, then the auto slack gets replaced.

:wink:

[Kranky]

Not sure if this is correct but this is what I was told.

Get on a hill and roll backwards tapping the brakes to cause the trailer slack adjusters to adjust.

Step on the brake up to 90 psi application to cause the truck slack adjusters to adjust.

Is this correct?

Auto slacks adjust as necessary when the brakes are applied and released.

It makes no difference whether the truck or trailer is stationary or moving forward or backward.

The brake application in reverse thing is for 4 wheelers.

[allan5oh]

Evidently you missed the second sentence in my post Allan:

And if I find one that is "way out" of adjustment, then the auto slack gets replaced.

:wink:

Your second sentence is irrelevant, because even if it is a "bit out" it should still be replaced, and the slack should NOT be adjusted.

[bob h]

You can adjust automatic slack adjusters but its a pointless exercise unless the adjuster isn't working or DOT is running a safety blitz and you want to make sure your brakes are "snug".

brakes don't need to be snug... they need to be in spec

many slack adjuster manufacturers (excluding a-m) recommend NOT adjusting auto slacks as it wears out the clutch mechanism

[bob h]

Where I work, whenever I have a truck in for PM, I'll manually adjust the brakes just to be sure that they're within spec.

And if I find one that is "way out" of adjustment, then the auto slack gets replaced.

an overstroked pushrod should lead you to the same conclusion without touching a wrench...

[roadranger]

In any case - if you adjust or repair brakes without being certified and that truck gets in an accident you're in a heap of you-know-what. The certification class is usually only one day and will teach you how to measure the stroke properly AND will teach you that it is NOT legal to adjust any brake adjuster without measuring the stroke afterwards and that it is NOT legal to adjust an automatic adjuster unless it has just been replaced or it had to be loosened to replace or work on something else!