Air brakes

[Gator48]

We are in our 3rd year of ownership and traveling in our 2006 Itasca Horizon. Retired last year and now have the time for the longer trips.

I always like to have a lot of stopping room so everything doesn't end up front because of a panic stop.
Last trip I had to make two rather short stops for brake lights and noticed if I feathered the brakes rather than hitting them hard I ran out of pedal at the end of the stop. In other words the pedal was hard on the floor with no travel left and the wheels were not feeling like there was anything left if I need to lock them up.

Will "pumping" air brakes give better braking or just use up air? With 36,000 miles I don't think the linings should be used up. I will probable get them checked, but I wondered what you all think.

input please.


Dave

[Gib3633]

vegasfood guy: Yes I know how to do an airbrake test. It was the result of a two day coarse at the local college. I'm not a qualified instructor but I have scored perfect each time I have to write. I also do the test completely each time I move my semi from the yard.
I purposely wrote the story as I did to stress the importance of not driving an unsafe vehicle and calling out a qualified truck mechanic. Here in Ontario the number 1 reason for trucks being grounded at the scales both CANADIAN AND US is brakes out of adjustment. I'm not trying to be a wise AZZ but any modern day truck driver will know exactly what I am talking about from the story I wrote. I've gotten into the discussions in the past and people who drove big trucks 40 years ago who clearly knew nothing were trying to make me the fool. One gentleman went so far as to say as long as the s cam didn't go over center there was nothing to worry about. That line of insults obviously came from someone who knew nothing but thought he knew everything.
The reason for our endorsement is not so we can do repairs but be able to recognize the problem ,take it out of service ,not drive it in for repairs but bring out a qualified tech.
An air brake system is relatively inexpensive to repair ,extremely reliable and last a long time unless contaminated with oil or grease.
When I got home from Florida this spring and it was time to get my semi in for it's annual inspection I found out all the rules of the inspection had changed. My understanding is that it was going to be standardized for all of North America. With the stiff regulations for big trucks I can't imagine it not spilling over onto Motorholmes.
One other thing I forgot to add to my list was the need to drain air tanks every day. Who would ever think of doing that when they have an air dryer??
I wrote the reply to make motorholme drivers who are not truck driver realize that there is more to it than turning the key , waiting for the buzzer to quit buzzing and stepping on the peddle .
Please reread a couple of times more . Because of the lack of clearance between the vehicle and the ground and the fact you can't check brake stroke travel without being under the vehicle it should be checked over a pit and addressed by a qualified tech. An hours labor may save your life and someone elses

[vegasfoodguy]

Gator48 wrote:
We are in our 3rd year of ownership and traveling in our 2006 Itasca Horizon. Retired last year and now have the time for the longer trips.

I always like to have a lot of stopping room so everything doesn't end up front because of a panic stop.
Last trip I had to make two rather short stops for brake lights and noticed if I feathered the brakes rather than hitting them hard I ran out of pedal at the end of the stop. In other words the pedal was hard on the floor with no travel left and the wheels were not feeling like there was anything left if I need to lock them up.

Will "pumping" air brakes give better braking or just use up air? With 36,000 miles I don't think the linings should be used up. I will probable get them checked, but I wondered what you all think.

Do you know how to do an air brake test? Instructions will be in your state CDL book. It sure enlightened me.

Terry

input please.


Dave

[Gib3633]

Here in Ontario Canada we must have an Air Brake Endorsement on our license to drive an air brake vehicle.
The first and foremost part of the questioning part of the test is what do you do if you discover something wrong which you have. There is only one answer and that is take it out of service and call a certified mobile mechanic. I'm 1600 miles from you but based on the information you supplied you have told me much more than you realize. Motorholmes historically travel 6000 miles a year. Yours is 9 years old with 36000 miles divided by 9 equals 4000 per year.
You're in your 3rd year of ownwership and your brakes are way out of adjustment. That tells me you haven't had it in for proper service or the service tech is not a certified truck mechanic or these brakes would have been manually adjusted by him.
With the type of driving you do with wheel chokes in place and parking or spring brake released and full air pressure you then do 6 or 8 full brake application until air is depleted and then let it build back up. This should be done each time you strike out. The other thing I will mention and this is backed up in some motorholme manuals is if it is equipped with Meritor slacks and you have had them greased with EP2 grease they will most likely not adjust themselves as the grease is too heavy . You need EP1 which is not that easy to find.
As far as adjusting them manually it is important to understand that every individual brake chamber has it's own individual allowable stroke travel and that information is available in air brake manuals from the States that require the brake endorsement and probably on line if you wanted to research it.
The Air gauge on your dash is a tool to be used to determine the following
Low pressure cut in and out
Build up time
Governor cut out and cut in pressures
Air loss over 3 minutes
Engine off and key on at 90 to 100 psi ,full brake application with stick between steering wheel and brake peddle and go around and measure the stroke travel at each brake chamber.
Quite frankly none of this means anything unless you know the values and the procedure for doing this.
Most people are too large or too old to be crawling around under a motorholme and it is far to dangerous in case an air bag decided to blow. That is why a shop with a drive over pit and a certified Truck and Coach licensed mechanic should be going over your coach properly at least once a year.

[wolfe10]

prstlk wrote:
A thought
here and please correct me if Im wrong. When going down any grade with the pak or engine brake either on or off. Or in traffic is to make firm brake pedal suppression and then release and repeat. Continued even moderate brake pressure can cause overheating or glazing of brakes. Opinions?

Your last sentence is the most telling. A single stop, even panic stop is no problem.

The problem occurs when one tries to use the service brakes (air or hydraulic) to control speed of descent on long grades. That WILL destroy brakes or even leave you without brakes.

So, the correct technique on long descents is to find the correct combination of gear and use of exhaust brake/engine brake to keep YOUR SPEED IN EQUILIBRIUM. That is you are neither speeding up nor slowing down without using your service brakes.

Where a lot of first time heavy vehicle drivers get in trouble is that they see a long straight road and ASSUME that they do not need to control their speed. The Equilibrium speed of a motorhome will be FASTER than a loaded 18 wheeler, SLOWER than an empty one-- just straight physics. So, if you are blowing by all the trucks, you are likely going too fast for the grade.

[Ray_IN]

prstlk wrote:
A thought
here and please correct me if Im wrong. When going down any grade with the pak or engine brake either on or off. Or in traffic is to make firm brake pedal suppression and then release and repeat. Continued even moderate brake pressure can cause overheating or glazing of brakes. Opinions?

That does not apply when in traffic or city driving. Air brakes have a slight delay from the time you press the pedal until the brakes apply, unlike hydraulic, which are virtually instantaneous. This slight delay in heavy traffic may slow your stopping distance enough to cause a crash. This US Army air brake training manual should be helpful.
Another is The Air Brake Handbook, while more technical, explains in detail how air brakes and entire system function.

[RayChez]

Mine will not lock up even IF you press the brake pedal hard. The ABS will not allow the tires to slide. But you do not want to pump the brake pedal because that will use up air from your reservoir. Just apply a constant amount of pressure and you will be surprised how fast they can stop.

[FormerBoater]

Canadian Rainbirds wrote:
Surprised that of all the suggestions to park on flat/level lot with trans in neutral, parking brake off, NO ONE reminded the OP to CHOCK THE WHEELS.

Good point, but if you are on a level surface and alone there is no real need to chock the wheels as no one is outside of the coach.

Also, many do not own a set of wheel chocks.

[Canadian_Rainbi]

Surprised that of all the suggestions to park on flat/level lot with trans in neutral, parking brake off, NO ONE reminded the OP to CHOCK THE WHEELS.

[jtessnm]

To adjust all four slack adjusters on a Spartan chassis the air pressure must be normal, the PARKBRAKE MUST BE OFF and the brakes FULLY applied 3 to 5 times. This is best done with the motorhome on a level surface , so no rolling, motorhome in neutral, engine running to maintain normal air pressure. It can be done with the coach slowly moving but the coach will stop abruptly.

[Gator48]

Greyghost,

Thanks I did what you suggested and the brakes firmed up a lot.

As I said I use the brakes very softly. I remember back to the old driver ed classes in high school...."brake and accelerate like you have an egg between your foot and the pedal". Often while moving around in a park I just idle around slightly touching the brake and hit the shift buttons to back up. So not getting the pressure to set the adjusters.

Thanks for the help everyone. I still plan to have them looked at anyway. The linings look great.


Dave

[Kayteg1]

AGAIN breaking, releasing and repeating is draining air from the tanks.
Compressor will rebuild pressure after a minute or 5, but not on the instant.
When you are in situation like that, learn how to hold the brakes without fanning.
Still first thing is shift to gear or engine brakes that will not require constant braking in the first place.

[prstlk]

A thought
here and please correct me if Im wrong. When going down any grade with the pak or engine brake either on or off. Or in traffic is to make firm brake pedal suppression and then release and repeat. Continued even moderate brake pressure can cause overheating or glazing of brakes. Opinions?

[Greyghost]

I have a Spartan chassis. The correct method for adjusting the slack adjusters is to let the air get up to pressure. With the transmission in "N" and the Parking brake on, depress the brake pedal to its max. There is no need to do it quickly just hard. Depress the pedal 2 or 3 times, you should see an improvement in the braking. This method may take a few times before the brakes are adjusted. I now do this every time I start up. I no longer have soft brakes

[Kayteg1]

I did not read via all the replies, but with air brakes you have some simple rules.
1 air brakes used in short time take the air from tanks with limited capacities.
Meaning fanning them will run the supply low and has to get you into troubles.
2 I don't remember precisely, but DOT apply pretty liberal rules to air brakes.
From top of my head, with engine off when you step on the brakes and don't loose more than 3 psi per minute >> you are good.
3. If in any doubts, take it to specialist. Brakes is not the items to learn by errors.
GOOD LUCK