Dumping Air Bags on the Scale

I just can't imagine a scenario where one would feel the need to set trailer brakes [and dumping trailer bags] while on a scale. But using the foot brake hard while on a scale can in some circumstances keep weight "pulled back" from the tractor or up against the tractor, depending on how the application valves are tuned and synced.

This wasn't as much of a problem until air suspension tractor and trailers came into being.

 

Thx for the post albert, I always knew they would change, no idea it would be that much!

 

I always shut the truck off in gear not setting either brake.

 

On well-built Cat scales and air suspension tractor and trailer rigs, you'll notice that after stopping with the foot brake, then getting off the brake, you'll see it roll forward about 2-4 inches as the weight-shift [that the stop and hold caused] neutralizes and balances back out.

 

Whatever you do, don't dump your air on a state scale, you be inna heap o' trouble. Years ago, before the scale dudes got wise, I knew guys that ran spread axle reefers and flats, and they had separate controls to dump each axle and the tractor, and it worked,,,for a while. Scale operators became leery of trucks with air being released as they pulled on the scale. I think that's why they say, or said, "don't set your brakes", as that can change your weight numbers, as well.

 

I knew a guy who did this. Had his air valve outlets plumbed so you couldn't hear them when he dumped. Idk how much he used this setup but was pretty slick.

 

It has nothing to do with dumping air. In the first example, the tractor brakes were set. That means that the scale platforms for the steers and drives had some sort of pressure because the six sets of brakes on those 3 axles don't all set at exactly the same time.

Solution, set only the trailer brakes, or no brakes. This assumes you don't have split axles

 

I guess you don't know your front axle doesn't have parking brakes/maxi's?