Poor braking

Thank you for the reminder and corrections.

You are right, there is not enough friction. I totally support your move for big friction.

Im just sorry the factory did not install big friction shoes in the first place and you have to spend all this money to get it the way it's supposed to be. Never mind some of my somewhat error prone postings, Ive always been told watch the details, that what gets me sometimes. The little stuff.

I look forward to your success in this war. There is nothing better than a truck that will get up and go the way it's supposed to and actually stop and behave the way it's supposed to. It's a very very nice truck and I want you to enjoy it.

 

Sir, Ive been thinking carefully. I have no more problem with anything with the momentary lapse of forgetting certain details for which you kindly reminded me.

I value and treasured this chance to participate in solving something that maybe I might help a little bit. I see that others have also helped you as well. When you get it running properly and safely and with way way better brakes I might add. I only ask you a small favor. Print out a small half copy of a mallard duck or maybe it's a drawing colored in by one of your children or someone in the family somewhere. Put that duck on the dash when you take it out for a spin to be sure those brakes are working. Consider that a strange (To some... ) way of taking me along for a ride. There is a long story behind the Mallard. But I for one at the end of the day look forward to seeing you very happy with a truck you will NOT be afraid of putting to work.

Good luck!

 

I don't know what to think.

Is the stroke lengths ok on the rods between the cans and pads? Maybe there are too short stroke bolts on there? Does that even make sense?

One final card I can think of but it's reaching for that last straw: The cams. If they are not the correct cams maybe they don't exert the forces needed to be effective in braking? Is bad cams even a experience in truck shops?

Let us know if the Reps find something. You would think that with all of this that truck should be a nice stopper by now. Again, Im officially out of ideas.

 

I humbly appreciate your thanks. And have a interest also in hearing from the Reps. They should know way more than little ol me.

You have mentioned in praise to your tag axles over and over again, what is it with those things that your regular drive wheels and steers don't have? Anything?

Do you think your engine is still applying go while you are on the service braking saying whoa?

Im out of KISS. (Keep it simple stupid) it has to be something really stupid and simple. But it's beyond me.

Rest easy tonight. Tomorrow is a new day for battle.

 

Has anyone activated the modulators or other tests for the ABS system? How much air pressure is at the chambers if you push the brake pedal to the floor as hard as you can? I think I would run some of the diagnostic tests on the ABS system.
Heck we had a truck come into the shop once that had weak brakes and it turned out to be a screw under the steering column was preventing the pedal from being depressed all the way. I have seen the adjustment rod adjusted wrong on FLD that did the same thing. Just to name a few.
Here is a few things that Bepco says to check for insufficient braking.

1.) Insufficient Brakes -Brakes need adjusting, lubricating or relining. -Low air pressure in the brake system (below 60 psi). -Brake valve delivery pressure below normal. -Wrong size actuators and/or slack adjusters. -Failure of part of a dual air system. -If remote mounted brake valve, check linkage.

 

You should see a lot more at the chambers that 25 psi, the contact pressure alone is 10 to 40 psi depending on the cans, so you should see at least 60 psi to 90 psi on a mild peddle use and full line pressure on a hard peddle use, not 25. Bendix says the contact pressure is just the pressure to overcome the springs and friction in the brake so the shoes touch the drums,

Abs has nothing to do with the shoes, changing them won't help much, there is a serious disconnect with the rep and the tech working on the truck with thIs issue.

The abs uses modulator valves to shut off, vent or depressurize the brakes and it could be a bad valve or the abs ecm telling one or a couple valves to vent or shut off the flow. Or it could be a few other things like a pinched hose or bad valve.

Nevertheless the pressure to the chambers are too low and that may be the problem.

So I would start a pressure check right at the chambers, do each one and write down the pressure, the work your way back to the brake valve on the floor. Go check the pressure before the abs valves, before the relay valve and so on, all the way to the brake valve.

You should see at least 60 at each device.