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Old 07-08-2010, 10:13 AM   #29
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Originally Posted by TXiceman View Post
The big thing that has not even been mentioned here is to change to winter air in the cold months and summer air during the hot months. Also have to consider high altitude air when driving in the mountains.

Iím currently in Buenos Aires. Itís winter here. Iím filling every available zip-lock bag with winter air and will bring them back for use this winter. Iíve got several more trips to South America before itís winter in North America. Iím hoping to have enough ďwinter airĒ saved up to fill at least one of my tires.

Do you have a suggested storage method for my ďwinter airĒ??? Will it keep in my zip-lock bags, or should I transfer it to something else? Do I need to keep it refrigerated so it's properly winterized?

Will the oxygen leach thru the bag, leaving me with pure ďwinter nitrogenĒ??? That would be great!

Please help me.

I may be able to collect a few extra bags of ďwinter airĒ that Iíd be happy to ship to you (at your expense, of course).

Thanks, in advance.

Take care,
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Old 07-08-2010, 11:35 AM   #30
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777, I'd bag that southern hemisphere winter air in zip lock freezer bags, they are heavier duty. Then carefully arrange them with he zip lock up (keeps the bags balanced) in a cooler filled with dry ice, you don't want the fresh winter air inside getting wet. You'll want to ship them via sea, because that 777 cargo hold will alter their atmospheric pressure. Once they arrive please be careful to acclimatize them slowly. Part of the aging process will be to allow the oxygen (and errant pollen particle) to slip past the freezer bag leaving pure, unfiltered Buenos Nitrogen-ous Aires. I can smell the freshness already.

Then from the remains of the dry ice, the dry ice condensed all the moisture in that sea air making wet ice, add some to a fresh glass of Bombay Blue Sapphire, sit back, and remark to yourself - ahhh, isn't this so much better than fretting about what's in my carbon blacks so long as enough is in them?

RV tire air is always such a major big religious experience with folks...
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Old 07-08-2010, 11:50 AM   #31
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Does anybody think that Michelin actually tested for correct air pressure?
Or were they standing around saying "that sounds about right, let's use that number.
I.E: Engine takes seven gallons, lets put in eight just to be safe.
Just throw away your owners manual and fill all fluids to overflow, heck, then everything will be
Where does it say to deviate in the Michelin RV Tires 32 page booklet? Anybody?
When do you believe manufacturers spec"s????? Oh, when you choose to follow the numbers. (that was humor)

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Old 07-08-2010, 12:25 PM   #32
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FWIW A few years ago I was someplace, can't remember where, talking to a tire engineer. He told me that the most accurate way to measure the proper tire pressure is with a Profile Gage. A device that when held up against the outside of the tire, at the point where the tire is on the ground, matches the profile of the outside of the sidewall of the tire. This is what the tire manufacturer is concerned with. This is what determines the amount of flexing that is going to take place. The PSI Gage is simply a more convenient way to arrive at the same setting. One would have to assume they know what happens after the tire warms up to operating temperature. You could load your axel and apply enough PSI to achieve the proper profile, not to exceed the Max PSI Rating. This should not happen unless you have overloaded the tire.
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Old 07-08-2010, 12:48 PM   #33
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Originally Posted by RVDude View Post
Once they arrive please be careful to acclimatize them slowly. Part of the aging process will be to allow the oxygen (and errant pollen particle) to slip past the freezer bag leaving pure, unfiltered Buenos Nitrogen-ous Aires. I can smell the freshness already.

Oh, yes! Exactly.

You know, that's why I've decided to only capture the air on my trips to Buenos Aires. I spend time in Sao Paulo, too. The winter air there is not nearly as good as in Buenos Aires. Buenos Aires has good air.

Thanks for the help, RVDude. One bag of "winter air" for you! PM me with shipping/billing info.

Take care,

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Old 07-08-2010, 05:24 PM   #34
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Took my MH to Freightliner to have the oil etc changed. Asked the service mgr to check the air in the tires and what pressure he would reccomend. Sidewall says 125lbs. He said we fill to 110. "I said sounds good to me" I expect to give them a good thump to see if they still have air at each stop. Beyond that, they will recheck next time through unless the coach sits a season. Put a lifetime of driving an 18 wheeler and seldom did anything different. Keeps me rolling!
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Old 07-08-2010, 07:49 PM   #35
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Just the the homework

First step review the plackard inside the MH, it should state the tire size, type and pressure for each axle.

Verify this type of tire and inflation, this is what the manufacturer determined was the "best" for the vehicle as it left the factory.

Given their ratings were driven by the marketing department it may not be YOUR best.

Next look at your sidewalls. Ours states to "increase pressure by 10 PSI if consistant speeds over 65 MPH", yours may have different items.

Confirm the rating of the installed tires to confirm they are same or better than on the plate above.

Once all that is done, and if the installed tires are same or better than the manufacturer requires you can now relax...a little...

Now the fun part...the HOMEWORK.
Look up the exact data sheet for the original tires, next locate the data sheet for the installed tires.

Are the installed tires rated for a truck or MH?

Data on the net indicates Goodyear had major issues with a couple truck tires marketed as MH tires, it seems the truck tires have a different design, they carry a higher percentage of the rating in load, but the stresses are intermittent as sometimes the truck is empty whereas the MH is usually running at the same (near higher end of tire rating) weight 100% of the time which stresses the tire differently.
Load up your MH to the on the road state and get it weighed, compare the axle weights to the manufacturer plate, make note of differences on a label and stick it to the plate for future use.

Now see how the original tires were inflated, the manufacturer states a given inflation for the original tire, from the data sheet you can see if the manufacturer has under/over inflated the tires based on their axle ratings on the tag.

They may have under-inflated to soften the ride (at the cost of safety, google ford explorer)

Your actual weight may be different, lookup the inflation specification for the installed tire and inflate to this as a minimum to insure the tire can properly support the load, any less and it is unsafe.

Now compare to the original tag, if the original was higher than the requirement or if the tire requires difference due to driving speed then make this adjustment to the starting number based on weight.

NEVER go over the rating of the wheels and ALWAYS use the weight rated PSI from the chart as the minimum.

If you cannot inflate with enough air to support the weight on the axle without exceeding the rating off the wheel then either the tires need upgrading, weight removed or speed reduced.
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Old 07-08-2010, 08:01 PM   #36
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Well, my tires are rated for 5205 lbs single, and 4805 dual at 110 psi

(Actual Weights)
My front axle is 9280 lb (Divided by 2 is 4640 each tire)

My rear axle is 26310 minus 9280 is 17030. (Divided by 4 is 4257.5) and that includes the TOAD hooked up

My gross is 29760 lbs at that weighing.

I was 208 pounds light of fuel so my actual gross was 29967.

And if it were applied to the rear and front axles, it would make them weigh 26518

I'll let you do the math, and tell me, what air pressure would you run?

Personally I'll stay with 110 psi for the safety margin.

I don't portrait to be an expert in this field, by any means, but I do the best I can with what I have. Other RV'ers can inflate their tires the way they want to. I hope they tend to be on the "safe" side.

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Old 07-11-2010, 10:45 AM   #37
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It is far more dangerous to run with a tire under inflated. As little as 10% under inflation is considered dangerous. That is only 10psi on 100psi tire. It also decreases fuel mileage.

It is considered bad for ride comfort and handling and may cause premature wear to run a tire over inflated. I believe it would have to be fairly over inflated to cause excessive wear and or poor handling. but at the same time can increase fuel mileage.

I would be far more concerned about running a tire under inflated then over inflated.

That being said, wives tale or not I run all tires on all my vehicle at or slightly above tire pressure values.

My Honda 5psi over on all tires.
My Silverado 10psi over on front (Plow) rear at recommended 80psi (bed is usually empty)
RV Front as recommended (120psi is max for tire and rim) rear 5psi over recommended.

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Old 07-12-2010, 01:14 PM   #38
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[QUOTE=InPursuit;666210]Good on you to mention the ambient temp factor.

As tires warm during the course of a day (friction and ambient temps both) their pressure tends to increase all on it's own.

Whether attempting to compensate for Texas summer heat is appropriate is a whole other discussion but If your starting point (cold, ambient) is significantly warmer than most areas then I'd suggest that adding more pressure at the outset is the OPPOSITE of what such an adjustment should be.

Think about that for a minute.

This is known as an anecdote. A thousand and one things (f'rinstance elevation changes) could be underlying the phenoma you describe occurring.

but using that anecdote as a basis to reinforce your own bias and preference to ignore objective recommendations and physics for that matter is sketchy at best.

Perhaps we are just lucky but we are in our 6th year, on our 2nd set of Michelin tires and have had no tire problems.

Perhaps so.

Meh. So long as it is consistent with your accumulated bias about which experts and which science aligns with that...

The tables provided by the various tire makers are "cheat sheets" so you don't have to do the math yourself.

Do the math yourself anyway. Start with a KNOWN set of weights.
Sorry, but I don't get your point at all here. My "accumulated bias???"

Let's go back and look at my original post.
- I got CAT scale weights
- I stopped and got DPS individual corner weights
- I compared the two and found them consistent. I determined that I KNOW the weight of the vehicle.

So - help me out here - what else is necessary to "Start with KNOWN set of weights?"

We use the RV all kinds of ways. We take longer trips (with extra food and clothing), we attend DOGs (Dutch Oven Gatherings) where we take along a lot of extra weight in cooking utensils, etc. I take people along camping and they bring things with them. I'm not going to go out and re-weight the RV every time I do that. So....I take a more conservative approach.
I know the base weight from my measurements and I add 5lbs per tire to compensate for the varying loads that I might have. That way, I don't have to "do the math" every time I turn the ignition key.

I always check the tire pressures cold and undriven. In Texas in the Summer, the ambient air temperature can be 80+ degrees F. If I were really trying to be precise, I'd figure out exactly how many pounds that I need to each axle, based on the adjustment that I should be making for the degrees above the manufacturer's ambient air starting point. I actually tried to do that when we first got our RV and found that the tire pressures were not following the changes that I would have expected based on the ambient air pressure change. I simply decided that it was easier to maintain the 5 pound per tire compensation rather than try to continue to mess with the ambient adjustment calculation. Bad on me.

I am not now nor did I in my original post represent that I'm taking a scientific approach to the matter of tire pressures. I'm simply following the recommendations of the tire manufacturer, based on my KNOWN weights and adding a "fudge factor". I figure that I have a range of 70lbs to 110lbs on these tires. My weights actually put the pressures (discounting any adjustments) at 85 and 90lbs. I run 90 and 95lbs.

So I really don't have a "bias". I'm not for or against anything. I've taken what I think is an informed approach. I weighted my vehicle, consulted the manufacturer's charts and acted based on that information. That was exactly the RVIAA safety recommendation that I received. Where the "wheels come of" of my process, according to your suggestion, is that I'm second guessing the the tire maker with the 5lb adder. Right. Actually, I talked to Michelin via telephone when I bought my first set of tires and told them exactly what I was planning to do. I documented it back to them in a registered letter. At that point, there were a lot of stories about XRV tires with sidewall blowouts and, if I had one, I didn't want them to claim that it was my fault. They called me back and verbally agreed with me that my approach was sound. I documented that conversation because they wouldn't. Fortunately for me, I've haven't had to use that information since.

Let's talk about down sides. We all understand that the down side of an under inflated tire is heat build up and possible damage. The down side of an over inflated tire (assuming that it is still within its maximum range as mine are) is abnormal tire wear. I will promise you that I will never wear out a set of tires on my RV by tread wear alone. I have a 5 year replacement policy, however foolish some think that is. It is my choice. In 5 years, I will not want to spend enough time on the road to wear out the treads. Ultimately, I don't care about tread wear on my RV tires. Yes, I do watch it and physically measure tread depth (I have a gauge) But I don't expect to see wear enough to cause me to replace tires within my normal 5 year cycle. So over inflation wear isn't a concern of mine. I will tell you that we carefully examined the first set of tires that I took off this RV for exactly that. Neither the tire dealer nor I could see any evidence of over inflation wear.

So please explain, in detail, exactly what I should be doing rather than simply telling me that what I'm doing is wrong and based on my "bias". I'll be happy to provide the weight information for my vehicle.
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Old 07-12-2010, 04:28 PM   #39
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Question--what kind of tire gauges do you use? Have you had it checked for accuracy?
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Old 07-12-2010, 07:18 PM   #40
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FWIW I have a Gage that was certified for aviation use. It corresponds exactly with my individual sensors for my PressurePro System, 10 sensors. I have also checked it with a few very inexpensive digital Gages, 10$ to 15$, that others have had, an they were all reading within 1 PSI as well. Of course the last accurate reading does not insure the next one is accurate. The agreement with the PressurePro is what I look for.
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Old 07-12-2010, 08:47 PM   #41
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Talking Fudge factor makes us crazy...

I get real crazy when i hear "fudge factor" it is usually used when determining batteyr plant or HVAC, after some questions being asked one realizes the person using the term has a difficulty applying a formula and getting the desired results, so a "correction" is added.

In the cases above, "safety factor" would be a better term as most of the posters fuly understand the concept.

Go to sends out to multiple engines, gets more stuff faster) and query about tires, there is a bunch of stuff there.

In short, as long as the rating of the wheels and tires (the SYSTEM) are not exceeded there is no safety concern with tire failure due to overinflation, handeling of the rig is a complete different conversation, there could be safety issues there if the tires are so stiff that the handling or braking is changed.

On the other side, slightly underinflated tires cause excessive sidewall movement creating additional heat to be generated. the sidwall tears out along the radius parallel with the tread, and the tire pressure was reported to be about 85 PSI with the load requiring 90 to 95 PSI.

Couple this with tires that may not be reted for the continous load of the MH then the need to insure proper inflation is more important.

Over is better, like I mentioned before, the weight of the rig against the manufacturer rating should be considered the MINIMUM, the only option is increasing the air for Fudge, Safety, fuel mileage or because it is Monday.
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Old 07-12-2010, 09:13 PM   #42
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As the OP, I'm still waiting for somebody to find the word MINIMUM in Michelins booklet.
If 5 lbs is good, wouldn't 10, make that 20 lbs extra be better?
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