I completed a round trip from FL to CA this past summer in my 94 Regency with the Spartan Mountain Master chassis, 300hp Cummins
and air brakes. The trip was trouble free but the brakes worry me because they seem soft. Especially on long downhill runs. My unit does not have a jake brake and I had to slow down to 20-30 mph on the long downhill slopes and still worried about over heating. It also has ABS. Whether hot or cold the pedal seems the same ---it almost bottoms out. All four wheels are drum brakes -- no disc.
Is there any kind of adjustment that I can experiment with?
I am a good shade tree mechanic but have no experiance with air brakes or diesel.
Also, would an exhaust brake system be recommended and what is the ballpark cost?

Thanks for any help.

I am the least mechanically inclined nor mechanically qualified person to post on this site...

However...

I recently had a problem with my brake-lights "hanging-on", even after shutting-down and exiting the coach. I intially trouble-shot in the direction of a "switch" or electrical problem.

...as it turns-out, it was the [now known] "Treadle Valve", which is the "valve" located directly below the brake pedal, bolted to and thru the bottom of the floor.

I too, could bottom-out my brake pedal and it did have some feeling of "softness", however, my brakes seemed to be stopping the coach without a problem. I would at times find the need to slightly "pump" the brakes, in order to build enough air pressure in the valve and to give a better "feel" at the foot pedal.

I could hardly believe the change in the responsiveness of the brakes following the replacement of the Treadle Valve. My brakes are so "tight" now, they will put you thru the windshield if your not careful ...very cool!

Anyway... this was a 300(+) dollar item and had to be ordered from Spartan. No problem with the brake-lights following the repair ...obviously, the brake-light problem was just an extended symptom of the chief complaint.

I guess this is something you could possibly consider.

I can't help with much except braking with drum brakes on long downhill runs.

Brake vigorously and slow down to half or 1/3 the limit. Let off the brakes and let the coach speed up, then apply again. This techniques allows the brakes to cool And doesn't heat them up initially as much as riding them.

quote:

Originally posted by Frank Strong:
Is there any kind of adjustment that I can experiment with?

The simple answer is to adjust the brakes at the slack adjuster. Each wheel position has an adjustment that you can make.



Picture 1 & 4 shows the brake at rest - no air psi.

Picture 2 shows air psi applied and the brake chamber pushrod and slack adjuster pushing to the left.

Picture 2 & 6 also shows what an out of adjustment condition looks like. Notice that it's past a 90 degree angle?

When air is supplied to the service side of the brake chamber the push rod and slack adjuster should be at a 90 degree angle - the proper position as what is showing in picture 5.

Picture 7 & 8 shows a front steer position. Notice the item that says "rotating cam"? When you step on the brakes the "S cam" (aka rotating cam) lifts up the rollers causing the brake shoes to make contact with the drum.

The adjustment is rather simple if you know what you're doing - you could train just about anyone to adjust brakes. The problem is doing it for the first time and getting a good handle on what you're doing.

The actual training requires a little hands on. By adjusting that bolt the "S cam" turns to send the shoes closer to the drum - once the shoes touch the drum and the bolt won't tighten up anymore then you back that bolt off a half a turn.

Step on the brakes and see if you have a 90 degree angle or no more than 1 and a half (1 1/2) inches of travel of the pushtube. If it's longer than that or the angle is off then have someone help you further.

When adjusting drive axles the parking brakes need to be released so they'll need to be made with full air psi.

Because the front brakes do not have a parking brake chamber attached to it, you can adjust them without releasing your brakes.

From slack adjuster being at rest to brakes being applied with your foot you will have no more than one and a half inches or a little less of overall travel and the angle should be very close to 90 degrees. At 90 degrees your force is at it's maximum.

The 1 and 1/2 inches is for a type 30 brake chamber. A smaller chamber requires closer clearances.

If any of this sound foreign, or your unsure, then leave it alone and call an expert in to help you. Pay someone - the life you save may be your own.

Several variables...
The adjuster bolt could be seized - the slack adjuster could be defective - the S cam bushings could be worn out - The shoes could be worn below min thickness - the main spring could be broken inside of the maxi chamber you could have severe cracking on a set of overheated brakes thus glazing them.

If anyone follows this advice you do so at your own risk. I repeat, pay someone to show you how to do it the first time.

Man ---- the feedback you guys have provided is right on the money!! Between the treadle valve and the S cam adjustment, I should be able to isolate my problem. And don't worry Bill, I have done enough drum brake jobs on autos to understand the risk of over adjusting the S cam. Too bad there is not some way to check the shoe wear without pulling the drums --- like disc brakes.

Were exhaust brakes common on diesel Barths? I test drove a used Fleetwood Discovery with a Cat/6 speed Allison while in New Mexico and was surprised at how well it braked the unit without the loud exhaust noise. I am surprised my Barth does't have one since these were top of the line RVs.

Special thanks to Bill for the great pictures and tutorial!

quote:

Originally posted by Frank Strong:
Between the treadle valve and the S cam adjustment, I should be able to isolate my problem. And don't worry Bill, I have done enough drum brake jobs on autos to understand the risk of over adjusting the S cam. Too bad there is not some way to check the shoe wear without pulling the drums --- like disc brakes.

Most soft pedals can be straightened out with a brake adjustment. Not that the pedal is really soft. It's just that your brakes could be so far out of adjustment that it just feels that way.

If you look around the backing plate you should see an oval port - it might need you to take a punch and tap it out... most of the time it's an open oval slit. Some times there's a piece of rubber in there you pull off.

If your slack adjuster is at 3 O'clock then your sight ports are at the 6 & 12 O'clock positions. This is where the thickest part of the shoes are located.

If you adjust your brakes in the wrong direction you could scoop out the brake shoe rollers. When adjusting look into the sight hole and make sure the brakes are going towards the drum.

I redid picture 8 to show the gap between the S cam and the rollers. If it gets turned in the wrong direction you can now see better how the rollers could get scooped out.

The correct direction of rotation in picture 7 & 8 only is clockwise to adjust tighter. Each position has a different direction of rotation and is related to s cam and brake chamber mounting - they do not all turn clockwise to tighten. Picture 7 shows what the shoes and the rollers look like on the high side of the S cam with the brakes applied in a clockwise rotation.

If you find you are using the brakes a lot going downhill...Downshift!!!! The old truckers rule of thumb is to go down a hill in the same gear that you went up it. Also they say you can go down a hill too slow a thousand times but too fast only once.

Bill, thanks again for your expert advice. I plan to work on this tomorrow and I'll let you know how it turns out.
Downshifting and braking as described still left me worried at the bottom of the mountain. I was down to second gear and 20 mph most of the time and was cookin by the time I reached the bottom of the valley in Yosemite. Thats why I'm so interested in the exhaust brake system. In theory, it should help reduce the demand on the brakes.

Another way to take it easy on your brakes is to get a copy of the Mountain Directory West or MD East books. They will tell you what the passes and steep grades are in both areas of the U.S. When i am going somewhere i sit down with a good atlas and my MD books and look to see what i am going to run into and plan my route accordingly. Well worth the money. Website is www.mountaindirectory.com I won't leave home without them......oh wait, i fulltime so i always have them with me!

"If you look around the backing plate you should see an oval port - it might need you to take a punch and tap it out... most of the time it's an open oval slit. Some times there's a piece of rubber in there you pull off."
Bill, I think you're incorrect on this; the Spartan MM has no backing plate.

quote:

Too bad there is not some way to check the shoe wear without pulling the drums --- like disc brakes.

My '97 has the Mountain Master w/325 cummins and 6-speed Allison; sounds exactly like yours, chassis-wise. My brake shoes are open to view (from about 4 O'Clock to 8) when I crawl beneath and look at them. The shoes are in profile, of course, and one doesn't see all of them, but enough to ascertain wear. They are very close to the drums; so adjustment needs should be obvious, as is wear.

Frank,
Absolutely install an exhaust brake. Installed price is less than 2k and that includes the exhaust valve spring upgrade and valve lash adjustment. The exhaust brake will hold you back on most grades without ever hitting the service brakes. It is also very handy on interstate off-ramps and any other time you need to slow the rig. Exhaust brakes funtion by inserting a butterfly in the exhaust stream after the turbo. All it does is turn the engine into a 60 psi air compressor during deceleration. All you have to do is downshift the tranny. For a few dollars more, an Allison dealer can program the tranny to do that too. The butterfly opens when you reapply throttle. Once the brakes get hot they are pretty much useless.

There is a slot in the backing plate that allows you to see the brake lining. Hope this helps. Billy T

quote:

Originally posted by Gunner:
Bill, I think you're incorrect on this; the Spartan MM has no backing plate.

If there's no backing plate then it'll be real easy to see how much shoe life and if he's turning it in the correct direction. I figured Frank's statement "Too bad there is not some way to check the shoe wear without pulling the drums" was telling me he couldn't see into his shoes.

Seeing that you have the same chassis, you would know how it's setup. I've got juice brakes on an Oshkosh Chassis so I'll defer to you.

quote:

Originally posted by billyt53:
Billy & Helen Thibodeaux
Carencro (Lafayette), LA
www.billyt.com

Checked out your website... When will it be completed?

Looks like we have another person to add to the "Well Of Knowledge"

BTW: Nice coach!

Thanks again for the continuing feedback!

I have checked the travel and the angle on the slack adjuster on all four wheels this morning and they all seems to be OK. None move past the vertical. I also removed one of the rubber sight plugs and the brake shoes seem to be OK also. The only thing that looked suspicious was the right front which looked a little oily. I haven't noticed any pulling or grabbing so I'm hoping its OK. Could the bearing oil leak into this area and cause problems?
So if the shoes and the adjustments are OK then I guess that leaves me the treadle valve as the likely culprit. I tried pumping the pedal as Medic37 mentioned but didn't notice much difference. I wonder if there is any adjustment for the treadle valve?
I also appreciate the feedback from Billyt on the exhaust brake system. I had no idea that other internals would need changing like the exhaust valve springs. I thought it would be a somewhat simple bolt on affair --- maybe something that I could do. Sounds like these systems put a lot more pressure on the tranny and I wonder if replacing brake shoes would be cheaper over time than repairing the tranny. I guess the justification is in the safety of avoiding overheated brakes.

quote:

Originally posted by Frank Strong:
I also removed one of the rubber sight plugs and the brake shoes seem to be OK also. The only thing that looked suspicious was the right front which looked a little oily...Could the bearing oil leak into this area and cause problems?

If you have a wheel seal leak this will give you less braking action. Have this changed out. What was the overall travel of the plunger when the brakes were applied?

quote:

Originally posted by Frank Strong:
So if the shoes and the adjustments are OK then I guess that leaves me the treadle valve as the likely culprit...I wonder if there is any adjustment for the treadle valve?

Yes, it's now sounding like your treadle valve. No, there's no real adjustment there.

quote:

Originally posted by Frank Strong:
Sounds like these systems put a lot more pressure on the tranny... I guess the justification is in the safety of avoiding overheated brakes.

You answered your own question. In addition to "possible" exhaust valve springs you can add possible torque converter, transmission interface, additional transmission cooler etc.

These add on will also marginally shorten the life of a motor with added valve train wear and exhaust valves. Like anything there is a little bit of a trade off. Just make sure that whoever installs it doesn't adjust it to give you "too much" backpressure.