On level ground, with the 450 HP Cummins idling at 700 RPM, transmission in DRIVE, should the parking brake hold the coach stationary or allow it to creep forward?
It should hold. In some states during the air brake test portion of the licensing exam, you must demonstrate that the parking brake will hold by gently trying to pull forward with the parking brake engaged.
What about in reverse?
When you apply the parking brake, you are releasing air from the two parking brake canisters mounted on the rear axle, one on each side. Releasing pressure allows the large springs to apply mechanical pressure through the slack adjusters to the rear brakes only. In other words, the parking brake is operated by spring pressure alone. There is NO air pressure involved other than allowing the springs to come into use. The parking brake is NOT an emergency brake and will NOT help you at all in case you overheat the service brakes. My parking brake will hold in drive on level ground but my U300 will creep forward if on the slightest incline. This is why it is so important to use chock blocks in front and behind a tire and with a connecting cord, you would have to drive over one to forget it. I have heard Foretravel chocks all vehicles on level ground at their plant. NAPA sells excellent rubber blocks for around $30/each or easy to make a set. If you are on an incline and have any doubts, have someone else place the chocks while you keep the service brake applied in addition to the parking brake. Please read the article as it describes the braking system better than I can. Especially important is working underneath the motorhome and the dangers of tinkering with the canisters. See at: Bus Nut Online - Articles Of Interest - Air Brakes / Air Systems - by George (http://www.busnut.com/artgm06.html)
Another good explanation and diagrams at: Air Parking Brake | RV Talk (http://www.rainbowrv.com/rv-talk/air-parking-brake.html)
But the best example of a side by side test of what some consider the "emergency" brake is shown in the video at: Google (http://www.google.com/search?hl=en&q=dd3+parking+brakes&aq=o&aqi=&aql=&oq=)
In the US, we can just pay for our RV and drive it away. Europe and a lot of Canada require testing to make sure owners are up to speed (so to speak) on the air brake systems.
Pierce & Gaylie
93' U300/36
HI, i have to put my 2 cents on this subject, IF your brakes are adjusted right, per DOT specs, and the springs are good in your brake chambers it will hold on a steep hill. If you have a problem with either one it will not hold . You can move the unit with the brakes on under power but you will know it, it will make all kinds of noise.
This is the way my coach is set up.
Ben 1999 u320
Mine works like Ben's. If I move it with the brake on I am giving a bunch of throttle. With just an idle no movement and in neutral I am very still hill or no hill. I park it in a hill at work and do chock it in case some 4 legged critter hits th button or two legged person does it by mistake.
I'm wondering what type of chalk will hold a 30,000 lb. coach. I had some of the hard rubber but hollow chalks about 6" tall that I used on my U-225, a pretty light coach. It rolled over those chalks like they weren't even there one time when I forgot to remove them on a slight down hill grade. The coach was in gear but running at an idle at the time. From that experience it seems to me that a very solid, rigid and large chalk would be required to prevent the coach from rolling down much of a hill.
My advice is make sure your parking brake works effectively. If not, get new springs. FWIW
Ones like this.
Wheel chocks, heavy truck, industrial by Checkers #2514 (http://boston.craigslist.org/bmw/for/2289975314.html)
Rick, I am sure those would work better than what I had used. I paid less than $50 for the ones I mentioned.
You asked.
These will do it, albiet expensive. I found large box of them at an antique truck show and have sold most of them. I'll keep 2 for myself. You will not drive over these.
I am currently using a concrete block in front of one set of duals and a second concrete block behind the same set of duals.
Morris, I would test the concrete block chalk. If you are parked on a paved surface, I think it is likely that the tires will just push the block along. When it setting with the chalks in place, start the engine, release the brake, put it in gear and see if the block will stop forward movement. I think you will find that the blocks are not the best idea. Of course please report back if it turns out that I am wrong. That happened once before.
Kent, you are right a block will get pushed. Try a brick as it should work better and you will need one for each wheel too. It is a stop gap, get good chocks as a back up.
My parking brakes were weak when I got my coach, but adjusting the slack adjusters solved the issue. Yes they are self adjusting type slack adjusters, but like most, they need checked every once in a while as mine did.
They are simple to adjust.
Can the slack adjusters be adjusted without pulling the wheels?
Yes, but you need to crawl under the coach with the brakes released, make sure you have wheels chocked well, but yes you can adjust with the wheels on. It is much nicer to remove the wheels as I did, as I wanted a real good and close look see at all the kill items relating to brakes, brake pads, slack adjusters, linkage, bearings, seals, suspension and just snoop around for what ever as there is a lot to snoop over. I get into such things as drive shaft, U joints, oil leaks, brackets, bolts and no end to all the fun things to learn, can scrape rust, repaint what needs it, Heck I can spend a whole after noon playing, ah, working under the coach.
Always a joy playing and learning a quality machine. ;D
I can probably arrange for you to have a grand time playing under our coach. Heck, we would even let you fix anything you wanted to pay for. We might even pitch in a coach buck for some shiny new parts. (1 coach buck = $1000 Wal-Mart bucks; kind of like "boat bucks" or "airplane bucks") ;)
Has anyone used this chock? What are your thoughts/comments regarding this chock?
Thank you.
Walmart.com: Camco Wheel Stop: Automotive (http://www.walmart.com/ip/Camco-Wheel-Stop/14504364)
Think you will find that light wheel chock used on light tandom axle trailers.
If you want to use wheel chocks on the motor home, maybe a large block could be used if you run quick before it rolls away. Think having a good parking brake would be a nice touch.
FWIW
Something like these: Rubber Wheel Chocks with Eyelets | AW Direct (http://www.awdirect.com/rubber-scotch-blocks/wheel-chocks/)
(https://www.foreforums.com/imagecache.php?image=http%3A%2F%2Fwww.awdirect.com%2Fproduct_images%2Flarge%2FRSB10.jpg&hash=4e3ffa62eb1de67782d71f07a7e813b1" rel="cached" data-hash="4e3ffa62eb1de67782d71f07a7e813b1" data-warn="External image, click here to view original" data-url="http://www.awdirect.com/product_images/large/RSB10.jpg)
And you want 4 per axle. i.e. 4 for drive axle and 4 for steer axle, front and rear of each outside wheel if level. And if you are on a hill and your brakes don't hold you, don't expect these to hold you either.