jwdemarest

Tire Air Pumps

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Most air systems on trucks, buses and MH's  that I have had any dealings with over the last 50 years cut out at or near 120 to 130 psi, and will not restart producing air til down to or near 90 psi. For this reason, I use a cheater device which I made to make airing my tires easier. The device consist of a pressure gauge and a trigger operated  valve. While in the process of airing tires, I set to high idle and walk around the coach from tire to tire checking the air pressure, my cheater is attached to the air hose and I monitor the pressure, my coach drier pops off at 125, so if the pressure reaches 123, I will relieve the pressure back to just below 120. My tires use 105 to 115 at different positions, so this method works great.

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tireman9   

Hopefully, you are adding less than 5 psi only a couple times a season OR LESS. If more or more frequently I think you may have a problem and it should be fixed.

I would also hope you are running a +10% cushion above the minimum inflation needed for your coach based on your measured load on the heavy end of each axle.

 

For example, 275/80R22.5 LR-H is rated 6,610 @ 120 psi  I recommend a +10% cushion but you should not exceed the 120 on the tire sidewall.

90% of 120 = 108psi   At 105 the capacity is 5,980# and at 110 the capacity is 6175 so if your measured heavy load is between 5,981 and 6,175 your minimum psi should be 110 psi and your set morning CIP would be 110 + 10% of 110 or 121 but you don't exceed 120.    I would consider a working range of 5 psi so as long as you have 115 to 120 psi all is good. You would only need to add 5 to psi if and when the CIP drops below 115.

If your load is lower than 5,981 to 6,175 you could, of course, have a lower CIP but you should still have a cushion in the +10% range. 

If your measured load is above 6,175 then you need to shed some weight or up size your tires or shift some weight from the heavier loaded area to a lighter loaded area of the RV.

 

 

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Brett,

The brake air could be easily regulated though I do not know the DOT regulations pertaining to this. There may be an upper and lower limit. My coach Hydraulic over Hydraulic as are many I suspect could benefit.

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manholt   

BillE.  My air brake sets itself at 65psi and I can't move coach until my air builds back up to about 75psi...my upper limit is 127psi!

Tireman, surprised that you said nothing about getting moisture in tires...ref: Air drier.

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Carl.

My coach will not move either until air pressure reaches 60/65 PSI. It is at that point the park break will release. Initially pressure was 90. My peak pressure now is 110 enough to air the tires.

Your air system at the ranch that you will replace needs some study before assembly and burying it. You do not want to do it with plastic that has glued joints. That part of it placed underground may not be a problem, there, but it can be a problem above ground. The combination of the glued joints, the oil and air internally create a condition discovered in numerous body shops around the country over time. The oil air mixture reacts with the glue and erodes the joints and ultimately failure and FIRE and an explosive condition. The pipe in and of itself will contain the pressure.

My thought is to use white PEX tubing and SharkeBite fixtures. The Pex can be bought by the roll and in thousand foot rolls. I woulds also use 3/4 inch 1 inch best as the pressure loss over a distance would be less. Fittings readily available at Home Depot or Lowes. Once you reach the barn or RV shed branch to smaller and with your talent it just requires a plastic tubing cutter and a screwdriver. Smaller sizes can be in colors like red or blue.:P 

Do not use steel, you know it rusts and copper it makes heat as the air travels through it. Heat of course will pick up any moisture condensed in the piping. It has been used extensively when a  drier is in the system. I use it in the body shop worked fine. It ro can be bought in long rolls, soft copper for water in well systems and under ground but expensive. Pex and SharkeBites may equal in cost.

 

B

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ObedB   

Carl,

In southern PA, air drying consists of charging the tank to at or near full pressure and opening the drain valve at the bottom of the tank before daily business starts.  Have a friend that turned wrenches for decades and said "bull____" when I mentioned the discussion about air dryers for shop air and tire work.

Of course, we are not in sub tropical coastal Texas. 

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tireman9   
On 10/22/2017 at 8:56 AM, manholt said:

BillE.  My air brake sets itself at 65psi and I can't move coach until my air builds back up to about 75psi...my upper limit is 127psi!

Tireman, surprised that you said nothing about getting moisture in tires...ref: Air drier.

Will admit I don't work with Class-A air brake systems but I assumed they have an air dryer system.   Do they? 

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32 minutes ago, tireman9 said:

Will admit I don't work with Class-A air brake systems but I assumed they have an air dryer system.   Do they? 

Yes they do.

Bill

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Yes if air braked, it will have a drier. I would assume a federal requirement. Yes well I just enhanced the air system on my coach so I have access to the "DRY" air for supplementing the air in the tires. On my coach only the e/park brake operates with air, the rest of it is for the air ride 8 air bag system.  Brake system is hydraulic over hydraulic.

BillE

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wolfe10   

Air dryers are not Federally required.  And, there are a number of SMC products that did not have them.  Will never forget draining more than 2 GALLONS of rusty water from the wet tank on a 1998 Beaver Monterrey (no dryer). Most all other manufacturers do fit dryers.

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jleamont   

I have worked in several shops in PA with poor quality air systems. Usually the design without a drop off will accumulate water in the lines between the compressor and work station ultimately send it into your tools or tires. I can remember the Firestone recall 10+ years ago working at a Ford dealer, airing up tires pulling the chuck away and shooting water two bays down, that was a common thing at that dealer and no one cared to do anything about it. Many tires left there with water in them.

I had one BMW come in from a quick lube place a few years prior with a horrible vibration, the quick lube shop pumped grease into all 4 valve stems and into the tires :lol: I scooped handfuls of grease out of those tires :wacko:. Told the customer to replace them, they wouldn't hear of it...just too expensive :ph34r:.

Someday I'm going to write a book of the stupid things I have seen in the automobile/truck and RV repair businesses over the years.

Back to the OP, I use the onboard system with a gauge/cheater device I built. I can purge the air off to trip the governor, watch it rise up on the gauge in my hand and reopen the air into the tires. 

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Well I decided this was a good time to use my favorite saying "you can never have to many tools".;)

I bought a pancake compressor off Amazon a DEWALT DWFP55126 6-Gallon 165 PSI Pancake Compressor. I also picked up a 3/8 in inline filter and dryer. We will see how good it does.

Yes I can use the on board compressor but that requires starting the coach every time to power the compressor. Which brings into play the whole "don't start your coach unless you are going to drive it scenario". Well that's my excuse.:D

Bill

 

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jleamont   

Bill have you tried it yet? Some of those small compressors just don't have enough CFM to handle a big job like that. 

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manholt   
Quote

Don't start your coach, unless your going to drive it.

Agree, but I leave after I have toped of my tires...your excuse is dead. :lol:  WBill, sometimes I wonder....how can a brilliant brain, be so wrong? :lol::lol: 

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2 hours ago, jleamont said:

Bill have you tried it yet? Some of those small compressors just don't have enough CFM to handle a big job like that. 

No I haven't yet. 2.6 SCFM delivered at 90 PSI also the 6 gal tank gives a small cushion. Should be good and it tops out at 165 psi so the pressure differential is better than some of the ones that only get to 125psi.

But Carl, now I have a new portable compressor. ;):D

Bill

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Try this, I will not tell what it cost, you guys will know I am nuts, but it is small and an obsoleted oilless compressor assembly new from Monaco. It is a main stream manufacturer U.S. made Pump,  motor is about 3 inches in diameter with a water filter bowl, auto dump, pressure pop off valve , plate and a spring suspension for noise and vibration dampening, top side rating 150 PSI. Many places to put it since it is only about 10 inches long 6 wide and 7 tall maybe 8. Like WBill I do not want to fire up the coach for short bursts so will retro fit this bugger to augment the system when engine is off and it is 12 volt. Will plumb in using push to fit fittings and tie it straight into the primary part of the air tank with a change in top side PSI to match the coach needs.

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FIVE   
On 11/2/2017 at 11:30 AM, obedb said:

Love air brakes in the mountains. Old truckers habit.

I'm not an old trucker, but I love engine brakes...in RVs that come air brakes, too.

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I have been using one of these for the tires on our coach:

     PORTER-CABLE CMB15 150 PSI 1.5 Gallon Oil-Free Fully Shrouded Compressor

With the higher 150 psi cut off it seems to have no problem adding a few pounds of air to top off the tires. I don't think it would be much good to fill a tire if it was 'really low', but then again if one of my tires is 'really low' I'm going to have the spare put on before going anywhere anyhow.

Got it on Amazon for around $100. I also have an outlet on the on-board air system I could have used, but I found it much easier to maneuver an extension cord than an air hose. It was really getting to be a PITA to drag out 50 feet of air hose and try and maneuver it to all four corners. This compressor is light enough that I can easily move it about, and the extension cord is something that we use often so it's always at hand. Of course, this method requires that the coach is either on generator or plugged into shore power.

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Brett, I suggest making the discussion of engine starting a new thread. I think it may turn into a good discussion that many may possibly miss because this thread started as a discussion on air compressors, (tire air pumps).

Just a thought.

Thanks.

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wolfe10   
4 hours ago, elkhartjim said:

Brett, I suggest making the discussion of engine starting a new thread. I think it may turn into a good discussion that many may possibly miss because this thread started as a discussion on air compressors, (tire air pumps).

Just a thought.

Thanks.

Done.  This discussion moved to: http://community.fmca.com/topic/11726-starting-cummins-ismisx-during-storage/

 

SO, any more discussion on that topic should be on the new thread.

Thanks.

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F454258   

I use a Baird 12v compressor on the road. Works well, very easy to stow. Bad news, have to run the engine.

My Mikita home compressor shows 125 lb output on the gauge, but will not pump more than 90 lbs of pressure.  How large a compressor, in pressure, do I need to inflate to 100 lbs. tyia

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