Community Forums

Cat320 · 12-25-2011, 04:55 PM

I have researched the 40 pounds of books that came with this beast, and I cannot find how the tires should be aired using the on board air. I have the hose and the found the fitting on the MH...do I just start the coach, let the air pressure build up, hook up the hose and do it? Will it take the pressure to 125 PSI? That's the way my AC powered compressor works...seems too easy.

Sidewinder · 12-25-2011, 05:17 PM

Thats really all there is to it but 125 lbs is probably the top of your compressors capacity so it will be slow. But why would you run 125 psi?

GaryKD · 12-25-2011, 05:18 PM

Hi Cat320,
Yep you got the process. 125 PSI might be the upper limit, just depends on your coach. Make sure the wheels can take that much PSI. Many have a 120 PSI limit. Try it and see.

texnet · 12-25-2011, 07:35 PM

Yes, you can do it that way but.... I doubt if all your tires should be inflated to 125 lbs. You fist need to look at the factory information that should be on a sticker/decal located inside your coach. Normally they are located on the wall about where your elbow is if you are sitting in the driver's seat. That is a starting place. The proper inflation pressure can be obtained by having your coach weight, best if you weight each wheel/dual wheel, but if not available then at least weight each axle. Once you have the weight then find the tire manufacturers pressure table and your axle weight.

I have a 44,000+ pound coach and my front tires are around 110 lbs, the drive axle is around 95 and the tag axle is around 85-90. When I had a new set of tires installed the installer inflated all the tires to 120 lbs... the coach handled and drove terrible! Once I adjusted the tire pressure it is a breeze to drive!

bdaball · 12-25-2011, 07:41 PM

Cat,
Not to complicate the excercsie but I might suggest you check out U-tube. There is an excellant video on this subject. Unfortunately I forgot the title.
The most importanat point to remember is that your compressor air system needs to be at a higher pressure point than the tires you are trying to inflate.
Example: If your tire is at 100psi and you want to raise it to 110psi, you need more than 110psi in your coach system. The video on U-tube does an excellant job of explaining this.
One way to accomplish this is to have a guage at the end of your hose prior to the nozzle. As the system in the coach is airing up watch the gauge rise. Now the important part. After your system completes airing up you should hear the bleed valve spit. Then and only then should you try raising the pressure in the tire. Another method is to have DW set in the drivers seat and pump the brakes to lower the pressure and cause the compressor kick on. Watch you gauge and only start airing up after the gauge is higher than the existing tire pressure.
Hope this helps. The U-tube video does a much better job than I.

Wayne M · 12-25-2011, 07:48 PM

I use the on-board air system all the time when I am on the road. The most my tires should be inflated to is 110 psi max. I used to run that when I did not know what my true weight was. So when low:

Hook up the air supply.
Use a reliable air gauge and check the tire.
Inflate using the on-board system to the desired pressure.
Check with gauge.
If to much, release some of the air.
If to little, add more air and in both instances check with gauge.

Mr_D · 12-25-2011, 09:10 PM

Our old front tires needed 125 psi, the wheels would only take 120 so Michelin sent me a letter allowing them to be run at 120 psi and use the 125 psi rating.
I found that my onboard air would NOT do it. I spent over an hour trying just to do the fronts. Finally gave up and bought a small 120 V. Coleman tank compressor that goes to 150 psi, although now I have bigger tires and don't need the 120 psi.

RVNeophytes2 · 12-25-2011, 09:38 PM

Quote:

Originally Posted by Cat320

I have researched the 40 pounds of books that came with this beast, and I cannot find how the tires should be aired using the on board air. I have the hose and the found the fitting on the MH...do I just start the coach, let the air pressure build up, hook up the hose and do it? Will it take the pressure to 125 PSI? That's the way my AC powered compressor works...seems too easy.

I looked up your tire size in the Michelin manufacturer's data.

If you don't exceed an axle-end weight of 5,375lbs front and 9,530 lbs rear with the 295/80R22.5 LHR XZA2 Energy tires, the optimum inflation dictated by the manufacturer is 75 psi. The sidewall limit is 120 psi. As for the sticker behind the seat, it refers to the bus at maximum weight, and might not even apply to the tires on it at delivery, let alone now.

But, don't listen to me or any other iRV2 member: have your rig weighed just as you use it and then communicate directly with the manufacturer of the tires that will be on it when you are driving.

sdennislee · 12-25-2011, 09:58 PM

See post 26 in the is thread http://www.irv2.com/forums/f258/what...-107949-2.html

Note: Post 34 in the same thread has the part numbers for the fittings, etc I used.

It has the youtube video from RVGeeks and a picture of the hose assembly I built for the task.

In the video you will note 2 people are required, the inside person fans the breaks to bring the air down so the compressor will kick. To eliminate the need for a second person I put and inline bleeder in my air hose so I can accomplish it single handed.

If you have any questions or need any help let me know.

Don't let them fool you it's not a slow process at all. You will be surprised how long it takes to take your air tank from 130 psi down to the point you need to refill. I can put 5 to 7 lbs of air in the 3 tires on one side, let the tank refill as I move to the other side of the coach. Once there it's ready to go. I haven't tried filling an empty tire yet.

It sure beats carrying 20 to 40 lbs of air compressor and giving up all that space. To save even more space I went 1/4" polyurethane air hose vs. the standard 3/8". 50' of it coils up to 8 or 10" in diameter and about 3 or 4' high. Plus the polyurethane remans more flexible in the cold.

BTW: I have a 35,000 lb coach when loaded and based on scale weight I run 105 front and 90 in each rear. I use the scale weight to find the correct pressure on the tire manufacturer's chart. Guessing at tire pressure can prove to be very dangerous. Corner weight should be your first choice at the scales, if the scales cannot give you corner weight then your second choice would be axel weight. If using corner weight use the heaviest weight per axel to determine air pressure. If using axel weight; divide front axel weight by 2 and rear axel weight by 4 (assuming duals). These 2 sums are the numbers you want to look up on the tire manufacturer's chart.

historyljc · 12-25-2011, 10:05 PM

Quote:

Originally Posted by RVNeophytes2

I looked up your tire size in the Michelin manufacturer's data.

If you don't exceed an axle-end weight of 5,375lbs front and 9,530 lbs rear with the 295/80R22.5 LHR XZA2 Energy tires, the optimum inflation dictated by the manufacturer is 75 psi. The sidewall limit is 120 psi. As for the sticker behind the seat, it refers to the bus at maximum weight, and might not even apply to the tires on it at delivery, let alone now.

But, don't listen to me or any other iRV2 member: have your rig weighed just as you use it and then communicate directly with the manufacturer of the tires that will be on it when you are driving.

I get mine weighed at the DOT scales right down the road. It's a little used one so they're glad to have the company. Any of the truck stops with a CAT scale will give you an axle weight which will do until you can get an axle end weight.

FormerBoater · 12-26-2011, 07:23 AM

Why not take the simple approach?

Get one of these:

Sears: Online department store featuring appliances, tools, fitness equipment and more

You can run this off of your inverter, you do not have to start your engine or genny and you do not need 2 people to complete this simple task.

Man that must be a rough ride at 125 PSI!

Dave
1998 American Eagle 40EVS

wa8yxm · 12-26-2011, 09:28 AM

To answer your question: YES!.. In fact you did a very good job.. you only missed one step. (And this is a one time step)

The very first step: Go to RV Safety, Merritt Island, Florida

Click on the link (Now near the top) for weighing your rig, They (For a very reasonable fee) come out, park your rig (With your help) on portable scales, and tell you what the PROPER pressure in each tire is.. Odds it is *NOT* 125 PSI.

Oh, and the LAST step: If your rig does not have a tire pressure monitoring system

The two best in my opinion are the ones by Smart tire, which must be installed by professionals and which won't fit on all toweds. and the Pressure Pro systems, which fit all vehicles and are user installed (you need only fingers to do the job, though you may need wrenches to get AT the job (Remove wheel covers on many rigs) Nothing like being able to check your tire pressure as your partner drives the coach down the freeway at 55 mph.. Actually.. It is exactly like that. And the first time it beeps at you to tell you the towed is developing a flat cause you have been screwed... So you air up the towed, and once you get to the tire store, they remove said screw and install a proper patch (Boot type) under the road hazard warranty at no cost to you and NO secondary damage to the fender well on the towed.. The unit has paid for itself, and it's replacement.

Cat320 · 12-26-2011, 11:21 AM

Thanks for the info guys. This is RV #5, so I'm aware of the method for determining how much air to put in the tires. The only reason I mentioned 125 is because that's the max it should ever take. I have no intention of putting that much it them now. As noted above, it would be very rough ride with 125 PSI in the tires and way too much pressure, especially in the rear tires.

justaroamer · 12-26-2011, 03:44 PM

FYI, do you have cruise control? Should work on most diesel chassis. If yes, do this for higher pressures, one person can do this. Confirm park brake is set and tranny in neutral. Start engine. Recheck park brake is set and tranny in neutral. Turn on cruise control and then hit resume engine should come up on RPM's, mine pumps up to about 145#. More than you need for tire inflation, but much quicker and only requires one person to do. At idle, only about 105-110# is all you will get.