Bad Day / Good Day

Now I'm going to have to "test" this, as I always just assumed that when you mechanically backed the brake off with the cage bolt, the service brake would not work at that wheel. Easy enough test to perform...release the trailer brakes and insert a cage bolt in one chamber. Jack up that wheel, and hit the trailer valve. See if that wheel still rolls.

In order to be OOS, 20% of the vehicle's brakes need to be defective. On a 5 axle truck, that means 2 have to have issues before you're sidelined. If you've only got 1 bad brake, you'll get written up and sent on your way.

And as for there being some rule that all drive axle brakes need to have park brakes, first I've heard about that, and using the power divider wouldn't meet the regulations even if it were a rule. You see, the regulations require the parking brake to be mechanical. It has to be able to hold the vehicle in place whether it has air or not, whether it has electrical power or not. Power dividers are normally open...and air locks them in. Air bleeds off, power divider unlocks, and those non-spring-brake drive wheels no longer have anything holding them. An electric lock also would fail if the batteries were removed or if they drained off and died. In either case, it wouldn't meet the parking brake requirements. It would also be cheaper and easier, if it were in fact a requirement, to just use another pair of brake chambers with spring brakes on them instead of the service-brake-only chambers, and run a couple air lines to supply the air to release the spring brake. The simple fact that a large number of trucks on the road only have spring brakes on 1 drive axle leads me to believe there is no such requirement to have parking brakes on ALL drive wheels.

 

There is an actuall requirment as to how many spring brakes are required. I've been trying to locate but not having much luck.

Heck , back when I started I had a 75 pete Coe. That truck came factory with maxi pots on front drive axle only. Our trailers were tandem axle highboys. These trailers didn't even have spring brakes. If the trailers lost air over the weekend it was real hard to hook up as they would roll away on ya. Had to charge with air before hooking up.

 

As for the rules that is just what I was taught in Rockwell or Eaton training class years ago. I do not recall reading it in a DOT regs. either. Some trucks definitely have spring engaged air released power dividers. Look at some IH's with the key on air up. The power divider lock light on dash even stays on in tell the parking brake is released. I do not like the design either nor do I know if all two double chamber trucks are that way. However if a vehicle is only required to have parking brakes on two wheels why do all 2 axle semi trailers have 4 of them anymore? Dogie hurt my feelings: I was living happily in my dumdness not knowing I was stupid.

 

Getting written up is really just as bad as getting put out of service imo. It's going against you on those all important safety ratings. If I have to ask I always figure it's best to just fix it right. I'm sure mtoo is not going to be riding around like that for the next several weeks anyways. Me, I'd drive it until I got back home, detour any scales I was concerned about and get on it asap back home.

 

I don't have any faith in TRP products. Pete dealer sold me a carrier bearing by TRP. "Much cheaper and lasts just as long" or something to that effect. Yup Six months later I replaced it with a brand name and had no more trouble. Have heard and seen other bad results.

 

thanks... I guess I learned something today. Just a tip on the brake cans... I really like the sealed lifetime ones. Up here in the winter ####, they make a HUGE difference in service life.

 

when you replace the one that is defective, go ahead and replace the other one on that axle. it is bound to fail sooner or later.

 

This is great advise right here.

For what it costs. If I got a spring brake that goes bad I replace them all. Then your good for 4-5 years again no problems.

 

The "maxi" can has two separate chambers and diaframs. The spring side has the large spring on the dome side to push the diafram and rod that goes into the service side of the can. The service side has the threaded rod that comes out with the mounting bolts and a diafram with a smaller spring that pushes the opposite way as the maxi side to retract the rod. Have you guys ever seen piggy back replacement chambers? They are quicker and easier to change, because you just undo the clamp and change air fittings, no need to cut and mount yoke to the rod.