Motorhome brake upgrade

[Kluckraft]

I have a 40' 2002 Beaver Santiam. I have never been entirely pleased with its braking capability. We are about to travel to the 5 National Parks in Utah and I was wondering if anyone has any suggestions as to how I might improve on my motorhomers braking capability so I can handle the long downgrades with more confidence. By the way, my tow is equipped with Air Force One. Thanks for your help.

Ken

[Kluckraft]

As a quick follow up, I had the PXRB installed last week and it has made a world of difference. In fact on a few of the 6-7% downhills, I actually disengaged as it was slowing me down too much. Thanks for your recommendations. Happy trails, Ken.

[Executive45]

DSDP Don wrote:
Kluckraft.....If you order the new PacBrake PRXB, order the two clamps that hold it on.....often the old ones have had it and the new ones are easier to work with. If you can access your exhaust brake, installing a new one is pretty simple.

DSDP Don, thanks for answering the OP's question back to me....

To the OP...I replaced mine in the campground using common hand tools in about 45 minutes....easy to do....Dennis

[DSDP_Don]

Kluckraft.....If you order the new PacBrake PRXB, order the two clamps that hold it on.....often the old ones have had it and the new ones are easier to work with. If you can access your exhaust brake, installing a new one is pretty simple.

[tiredkid]

Kluckraft wrote:
Thanks for all of the input...I am going to try the Pac Brake upgrade to my original OEM exhaust brake. Again thanks to all and safe travels.

Ken

best heed my advice an make sure its just not seized up as seen a few like that

[Kluckraft]

Thanks for all of the input...I am going to try the Pac Brake upgrade to my original OEM exhaust brake. Again thanks to all and safe travels.

Ken

[BigSkyBob]

mtrumpet wrote:
If you're unfamiliar with the Air Brake Test, here it is. This is the standard proceedure. (This was posted by foosh1 here on the forum back on 3/2/10)


1) Start vehicle and let pressure build up to proper level (usually 120 psi)

2) Leave parking brake engaged, put trannie in D and gently press the accelerator. It's called a tug test, and parking brake should hold the vehicle.

3) Stop engine, but leave key in whatever position that allows you to read your air pressure gauges, chock vehicle if necessary and release parking brake.

4) Press brake pedal very hard and start timing one minute. Watch gauges and check to see you don't lose more than 3 PSI in one minute (4 psi for a combo vehicle). Listen for leaks.

5) Start pumping the brake pedal rapidly, and you'll hear air bleeding off. When PSI drops below a certain level a warning buzzer should sound, and when it drops a little lower the parking brake will automatically pop out. (This is a safety feature that allows you to stop if you were to lose your service brakes).

6) You're done.

NOTE! It is very important that you NEVER press on the brake pedal hard while the parking brakes are engaged. You could damage the springs that operate the parking brake system!!

The last part of this post isn't entirely true. Modern air brake systems employ an anti-compounding valve to prevent excessive air pressure in the brake chambers.


Anti-Compounding valve is a relay valve with a double-check valve built into it

To see how anti-compounding works, let's use the example where a truck is stopped on a hill, and while the driver holds the foot brake, the driver also sets the parking brakes. Setting the parking brakes would normally release the air from the spring brake chambers which would allow the powerful spring inside the spring brake chamber to push the slack adjuster which sets the spring brakes. This all happens while the service brake chamber is already pushing on the slack adjuster to set the service brake. This combined force of spring brake and service brake force is additive and puts excessive force on the slack adjuster (the sum of both forces), which can lead to premature failure of the slack adjusters, or mistaken automatic slack adjuster over tightening.

One supply port of the anti-compounding valve is connected to the parking brake valve, and the other supply port of the anti-compounding valve is connected to the rear axle service brake pressure signal. Pressure from either source will activate the spring brake relay valve and fill the spring brake chambers, thereby releasing the spring brake. Therefore, in the above situation, the driver holding the service brakes on the hill, places service brake air pressure into the service brake chambers which set the service brakes. When the driver now sets the parking brakes, the anti-compounding valve still holds pressure in the spring brake chambers, from the foot brake pedal service brake supply port; even while the parking brake valve supply port has purged all air pressure to the parking anti-compounding supply port. This air pressure into the spring brake chamber, holds off the spring force from the spring brake chamber as long as the service brakes are applied, and only the service brake air chamber force is applied to the slack adjuster. This is anti-compounding, when the spring force is delayed while the service brake force exists.

After setting the parking brakes, and when the driver then lets up on the foot brake pedal, the service brake supply port of the anti-compounding valve looses air pressure, and the parking brake supply port still has no air pressure. Since the spring brake relay valve now sees no signal air pressure from either supply port, it quickly vents the spring brake chambers which set the spring brake force on the slack adjuster. So the service brakes stopped holding force on the slack adjuster at the same time that the spring brakes commenced to hold force on the slack adjuster. This is continued anti-compounding control of the brakes.

If the driver were to later step on the foot pedal after the parking brakes were on, the service brake pressure signal would go to the service brake supply port of the anti-compounding valve, and fill the spring brake chambers to release the spring brake force, at the same time as the service brake air chamber applies more brake force on the slack adjuster. So now, as the service brake force increases, the spring brake force decreases. This is also anti-compounding, when the force from the spring brake chamber is reduced to compensate for the additional force being applied by the service brake chamber.

[tiredkid]

Kluckraft wrote:
I have a 40' 2002 Beaver Santiam. I have never been entirely pleased with its braking capability. We are about to travel to the 5 National Parks in Utah and I was wondering if anyone has any suggestions as to how I might improve on my motorhomers braking capability so I can handle the long downgrades with more confidence. By the way, my tow is equipped with Air Force One. Thanks for your help.

Ken

I would strongly suggest you have your EB checked to make sure its not seized open.Happens a lot.The Activation lite will be on and trans will downshift making one think the EB is working but in reality its not.Seen this more than once

[two-niner]

Ken: When approaching a long steep downgrade the number one thing to do is slowing your forward momentum BEFORE you start going down. (let off the throttle ahead of time)

Otherwise it's a dog chasing its tail, and the tail (desired speed) never gets caught. We have visited those parks at least every other year and other drivers do not expect you to be able to maintain the speed limits. Do not worry about other traffic, stay in your lane and use your flashers.

Kerry

[Ivylog]

Kluckraft wrote:
Thanks. I do have an exhaust brake which helps a lot, and I have hade the pads and air recently checked. The problem I have is on long, steep descents the brakes get very hot (smoking hot), and begin to fade. This is with the exhaust brake on and in low gear.
Ken

I'll assume you have a Cat 3126 and a 6spd Allison. I find it hard to believe you were in 1st gear or even 2nd. When you turn on the exhaust brake what number comes up in the Allison shift pad? If it's only 4 then you can have it reprogrammed to have it go all the way down to 2. You can also manually down shift it below 4... rpm needs to be below 1900 before you manually make it shift to a lower gear. Brake hard to get it to 1900, manually select one lower gear and then get off the brakes. If in this lower gear your rpm's get above 2400 and the end is not in sight then you have to get on the brakes hard and repeat the above selecting an even lower gear. Usually you need to come down in the same gear that it took to go up. The Allison key pad should tell you which gear you are in.
My 98 Beaver Patriot had air over hydraulic disk brakes and I never felt they were as good as the air drum brakes I was used to, BUT I never had any problems coming down long grades out west as the exhaust brake and a low enough gear made where I rarely had to use the service brakes.

[wa8yxm]

Do you tow a trailer? (For example a car towed 4-wheels down) do you have a brakign system on said trailer (or car towed 4 down)

If not: you have your answer.. If the motor home has air brakes and the slave fits the towed M&G air/hydraulid system is my recommendation

For other configurations (Either no air brakes or slave won't fit) US-Gear unified brake decelerator or ... Ready Brake.

[DSDP_Don]

Fire Up.....The PRXB by PacBrake closes/restricts your exhaust even more than the OEM model. It has a small hole in the center of the flapper that stays closed, giving you more braking. The cover on the small hole is spring loaded and will release without damaging the engine.

I added one to my ISL....it gives more braking power at lower speeds than the OEM brake, but isn't much different in the 55-60 mph range.

[FIRE_UP]

Executive wrote:
On my Dynasty, I dumped the OEM exhaust brake and replaced it with the PXRB from Pac Brake. By far, the BEST upgrade I ever did. The difference was night and day. Spend a few bucks and upgrade....you'll thank me afterwards.....Don't wait too long to apply the EB. Lots of folks wait until their speed is too great before applying the EB. This means the EB does not engage. If 50mph is your comfort zone, apply the EB near the top of the hill just as you start down. The tranny indicator should show 2,3 or 4 depending on how it's programmed...yes, it can be changed. This does not mean your tranny has shifted, it simply means when your speed comes down it will lock in at that gear. The allison will not let you overrev the engine. If you begin to exceed your comfort speed, STAB the brake pedal and release. Do it as often as you need to in order to bring your speed down to your comfort level again. I rarely used my service brakes after the upgrade to the PXRB. ...Dennis

Dennis,
Just wondering, what exactly IS the improvement between the stock exhaust brake and the one you "upgraded" with? I mean, to me, an exhaust brake is and exhaust brake. All it does is close off the exhaust to build up pressure in that portion of the exhaust system so the engine cannot breath normally and has a ton of back pressure. Now, unless the factory one, like I have, is not closing all the way, which I'm assuming it is, then what good would it do to change to the one you went to? Again, just wondering.
Scott

[Executive45]

On my Dynasty, I dumped the OEM exhaust brake and replaced it with the PXRB from Pac Brake. By far, the BEST upgrade I ever did. The difference was night and day. Spend a few bucks and upgrade....you'll thank me afterwards.....Don't wait too long to apply the EB. Lots of folks wait until their speed is too great before applying the EB. This means the EB does not engage. If 50mph is your comfort zone, apply the EB near the top of the hill just as you start down. The tranny indicator should show 2,3 or 4 depending on how it's programmed...yes, it can be changed. This does not mean your tranny has shifted, it simply means when your speed comes down it will lock in at that gear. The allison will not let you overrev the engine. If you begin to exceed your comfort speed, STAB the brake pedal and release. Do it as often as you need to in order to bring your speed down to your comfort level again. I rarely used my service brakes after the upgrade to the PXRB. ...Dennis

[imgoin4it]

I came down a 6 mile long 6% grade yesterday, To come down that long foe that steep a grade without using the service brakes I had to come down at 39 miles and hour and in 3rd gear. If I went up to 40 MPH my coach would shift into 4th gear and I would have to stab the service brakes to get back under 40. Just start down slow enough and you should not have to use the service brakes at all if everything is working as it should be. Just have to "learn" your coach. With that said there are times I would sure like to have a Jake brake rather than just and exhaust brake.