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Air Pressure and Air Brake Loss

Yahoo Message Number: 69143
Two questions. Since the inside dual tire heats up more than the outside tire, causing it to have a higher pressure while traveling, does it make sense to inflate it to a lesser amount than the outside, realizing that while cold there will be a discrepancy?
Next, on the toad brake systems (such as the Roadmaster) that tie into the coach air brake system, what happens if you have a sudden leak or loss of air in the air line running to your toad or at a connection?

R. D. Vanderslice
Sob

Re: Air Pressure and Air Brake Loss

Reply #1 –
Yahoo Message Number: 69161
Hi R. D.

Answer One. According to Smartire readouts the inner duals typically run higher in the 1-4 PSI range as a result of higher temps (up to as much as 15-20 degrees in the extreme) depending on ambient air temps, sun, etc. I generally set the inners 2 PSI lower when I set them up cool, at 70 degrees ambient. That mostly levels the differential.
Answer Two. IMHO don't tap your coach air brake system. Use another product. I do . . . one less worry.

--

Lee Zaborowski

07 Intrigue 12153, Cat C-13

Re: Air Pressure and Air Brake Loss

Reply #2 –
Yahoo Message Number: 69168
Thanks Lee, looks like you may be the only one with an opinion or knowledge of the air leak issue on toad brakes. What you say on the tire air differential when cold makes a lot of sense. As far as air brake systems on toads being connected to the coach's air system, isn't that a fairly common option offerred by SMI, Air Force One, Roadmaster, and a couple of other manufactors. I have just never heard of anyone having an air leak between the coach air brake line and the toads air brake line and what the results were if anyone did. I have heard, through a not very reliable source, that you will come to a sudden stop in the most inopportuen place and possibly putting you in danger. Still looking for anyone with knowledge of what happens if your air brake air line from your coach to your toad decided it wanted to spring a mild.leak. Any one had that happen? I ran the roadmaster system on ny 06 ALLURE for 5 1/2 years and it workded fine. I can only summuize that they do work well and are for the most safe and problem fee until thy start gettig older, and then may be potentially dangerous headache. I guess no on this forum knows anyone who uses one of these systems and has had an issue with leaks or a sudden stop due due to the breaks locking up on their coach R.D. Vanderslice

SOB with Brakemaster air brake system.

Re: Air Pressure and Air Brake Loss

Reply #3 –
Yahoo Message Number: 69170
RD,

I don't have any experience with a loss of air but I was led to believe that the minimal loss of air from a toad hose failure would be compensated by the coach compressor. The Coach brakes only lock up when there has been a drastic loss. Usually, you will get air pressure warnings on the dash well before the rear brake springs clamp down the shoes.
I'm sure someone else is more knowledgeable but in the mean time here is a link to some good information about Air Brakes.
http://www.lowestpricetrafficschool.com/handbooks/cdl/en/5/1
John

05 Inspire #51399
10 Ford Escape
M&G Brake Sys.

Re: Air Pressure and Air Brake Loss

Reply #4 –
Yahoo Message Number: 69171
A mild air leak will be made up by the air compressor. Unless one is really watching your air compressor cycle then one will not notice. CDL air testing requires one to pump up the tanks full, shut off engine with full brake application and watch for air pressure drop. There is an acceptable rate allowed, just do not remember it. This would be a good test for all systems to check for leaks. Another indication is empty or very low air tanks after setting.

As for tapping in for toad brakes, I would tap in with a tee and check valve at the rear service brake quick release valve. As for sudden stops. Doesn't happen that way. With a total brake line rupture, it takes a little time for the air to drop to 60 lbs where the spring brakes start to come on, then the brakes come on gradual and brings the rig to a safe stop. All this gives one time to pull off the road if nothing else. This has been learned from experience from being around a school bus fleet for 19 years.

Leonard

97' Magna 5418

Re: Air Pressure and Air Brake Loss

Reply #5 –
Yahoo Message Number: 69172
In answer to your air brake question, if you have a break in the line to the toad, nothing much will happen. The volume of air that passes through the line isn't much. Air is not in the line until you apply brakes. I have played around with the system by placing a air chuck in the female fitting on the coach, starting the coach and applying the brakes. At engine idle and my foot on the brakes you can tell there is air escaping from the chuck but the engine compressor kept up. After the initial drop in air pressure when the brakes were applied, I saw no further pressure drop. In order for the brakes to apply for lack of air, you have to get the pressure down into the 60 pound range. A break in that line is the least of my worries.

Don

'02 Intrigue #11427
'02 Intrigue #11427

Re: Air Pressure and Air Brake Loss

Reply #6 –
Yahoo Message Number: 69174
Great info, John. I had been told about the same thing that you noted and hopefully we will never have to experience anything like that. Thanks for your input.

R. D. Vanderslice
Sob

Re: Air Pressure and Air Brake Loss

Reply #7 –
Yahoo Message Number: 69175
I have used an M&G brake system for years with no problems at all. The air line for it and the other brands taps into either of the air lines to the rear brakes with a "T" fitting. This is the same type as used through out the entire air system and is completely reliable if installed correctly.
An air leak will apply your brakes suddenly but not without warning as DOT regulations require air pressure gauges for notification and a loud buzzer that sounds long before the brakes lock. If this was a commercial vehicle the warning system would be one of the things tested at every DOT inspection. The inspector makes you pump the brakes until the air pressure drops enough to set off the alarm. He also will have you apply the brakes and watch your gauges to determine if you have a leak in the brake system. We should all do both of these tests regularly with our coaches.
Your air system is a dual system, one side maintains the coach air pressure and the other is for the brake system. It is very unlikely that a slow leak in the toad system or connection will cause a system failure while driving because there is no air pressure in the line until you apply the brakes. A leak here will not do anything to the main air supply until the brakes are applied.
If you want more information regarding air brakes pick up a commercial drivers test booklet from your local Department of Motor Vehicles, it will include detailed airbrake instructions because that is now a requirement for the commercial drivers test.

I highly recommend the M&G if it fits your tow vehicle.

I hope this helps explain how the system works.

Jim Hedlund

2000 Allure 30413

Re: Air Pressure and Air Brake Loss

Reply #8 –
Yahoo Message Number: 69176
Leonard and Don, thanks. I guess I won't worry about that possible situation again, but I bet I can come up with something else to worry about, like the Saudi's revolting, etc.. What a great group! We're hitting the road in the morning. Time to get rolling gang.

R. D. Vanderslice
Sob.

Re: Air Pressure and Air Brake Loss

Reply #9 –
Yahoo Message Number: 69201
RD

I would think that you already have an air chuck at the rear of the coach. When I was towed the tow truck operator used the chuck to bring the coach up to ride height for towing.

Dan 2006 Allure 31348 (with air chuck in rear)

Re: Air Pressure and Air Brake Loss

Reply #10 –
Yahoo Message Number: 69224
Thanks Dan, and everyone who responded. I feel a little less apprehensive now about using the coaches air system for the toad brakes. We're in Tunica, Mississippi at Harrahs Resort RV Park. This is a very, very nice RV park for anyone traveling this direction. I bet a whole dollar last night in a slot machine and quickly lost it, but did win big time at Paula Deen's seafood buffet, eating way too much! Had to run 6 miles this morning to work it off. We're making a loop from Texas over into Mississippi, then to Heritage down in Orange Beach and ending up at the CC Texans Rally in Breaux Bridge/Henderson Louisiana. Let the good times roll.

R. D. Vanderslice
Sob

Harrah's, Tunnica Mississippi