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Old 08-26-2009, 03:21 PM   #15
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I tested them when they were cold and then put them at 80 psi. I haven't had any problems since and unless someone can tell me that that is not the right thing to do I will keep them at 80.
WilliamJ -- sorry that most of the posts don't respond to your question. I kinds of threw the discussion off when I assumed you were talking about trailer tires as Chinese tires are much more likely to be seen on trailers than on motorhomes.

The only way to know what your tire pressures should be is to weigh the rig loaded as you normally travel, then check the tire pressure chart that your tire mfg publishes for your particular tire (normally available on the internet). Most motorhomes require slightly higher pressure in the front tires than in the rear.

For example, on my 40' diesel coach, GVWR of 32,000 lbs, last time I had the coach weighed the front axle was apx 11,500 (5,750 per side) total and rear very close to the max axle rating 20,000 total (10k per side). (because we were near max weights we did put the coach on a diet!!). I have Continental HSL tires, 275/80R22.5 LRH. For those weights, the mfg tire chart tells me I need to be running 100psi on the front and 95psi on the rear. Different brand & size tires require different pressures for the same weights. When I had Michellin XZA2 tires the correct pressures for the same weights would have been 95 on the front the 90 on the rear. Max sidewall pressure for these tires is 120psi, so you can see that my tires are rated for more capacity than my axles are, and if I inflated them to the max sidewall pressure they would be overinflated, which would affect both ride and handling.

I have no idea what your coach weight ratings are, how much weight you are carrying, or what brand and size tires you have on your 35' motorhome, so I don't have a clue if 80psi is just right, underinflated, or overinflated. My first guess on a 35' MH would be "underinflated," but I could just as easily be wrong. No one call tell you what the correct pressure is unless they know all that information.

If the "treads are loose" as you indicate, you likely need new tires before you take another trip. Whether the tires are coming apart or not, you need to know how old they are based on the date code stamped on the sidewalls. The last two digits indicate the year the tires were mfg'ed -- 6 to 7 years is beginning to push your luck even with good tires. With Chinese built tires, that old is really asking for trouble!

Hope this is more helpful is answering your questions. Good luck!!
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Old 08-26-2009, 03:46 PM   #16
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aschuerg -- welcome to the forum!

Kind of off topic the original question, but...
Quote:
(Nitrogen) humma humma humma etc ... and is used in all military jet aircraft tires.
I'll remember that next time I drive a miltiary jet aircraft, meanwhile, 100% nitrogen use in POV tires has been beat to death on most RV forums with little if any real proof it does anything close to all the claims or worth the cost to the end user. Read the research of unbiased researchers not connected with selling nitrogen, think about the claims in relation to the scientific knowledge you already have, then make your own conclusions. I will admit it is a great $$ maker for vendors who can convince people they need it. I'll continue to use the 78% nitrogen my normal air compressor puts out, and yes the compressor has an air dryer. ...and my tire pressures stay quite constant too. And even if you use 100% Nitrogen, you DO STILL NEED TO CHECK YOUR PRESSURES regularly, either manually or with a TPMS, as nitrogen leaks out of holes in tires just like regular air does.

Quote:
A properly pressurized Class A tire should see in excess of 120k miles before replacing is required
True, but that has nothing to do with using 100% nitrogen -- not that most of us are likely to drive our RV tires that many miles. Properly pressurized tires have seen that many miles for years on OTR trucks w/o benefit of 100% nitrogen.
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Old 08-28-2009, 05:56 PM   #17
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[QUOTE=Elkhartjim;538205]This thread is unbelievable to me. If you don't know what your mh weighs then you can't possibly know what the tire air pressure should be.


My tire pressures increase dramitically with ambient temps... maybe your tires arent made of rubber
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Old 08-28-2009, 07:20 PM   #18
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[QUOTE=georgetown350;539172]
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Originally Posted by Elkhartjim View Post
This thread is unbelievable to me. If you don't know what your mh weighs then you can't possibly know what the tire air pressure should be.


My tire pressures increase dramitically with ambient temps... maybe your tires arent made of rubber
Huh! I need to understand this because there is definitely something I'm missing. First, since you quoted my post, what does ambient temp have to do with how much your rv weighs. Are you saying that the hotter it gets the more your rv weighs? Second, now this is where I really get confused. You check the air in your tires that are made of rubber and its lets say 100 degrees F and the pressure reads 50 lbs. Later that day it get cold enough to freeze the lake, are you saying your tires are not at 40, 30 or lower pressures. I will agree it may fluctuate a few pounds but "dramatically" I don't see. I may be all messed up on this but now I don't know at what temp I'm suppose to inflate my tires to the recommended pressures. Goodyear doesn't say 90 lbs at 80 degrees. Please help me understand.

I do stand by my quoted post,"you need to know what your mh weighs to know what air pressures to inflate to". Regardless of the ambient temp.
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Old 08-28-2009, 07:59 PM   #19
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Check out this link from Bridgestone. It will dispel all myths about ambient air temperature AND altitude.

Untitled Document

In other words-----check your tire pressures cold!

Check your tire pressure daily.
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Old 08-28-2009, 08:56 PM   #20
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Originally Posted by Tom and Patty View Post
Check out this link from Bridgestone. It will dispel all myths about ambient air temperature AND altitude.

Untitled Document

In other words-----check your tire pressures cold!

Check your tire pressure daily.
Excellent article, thanks for the post. I was surprised they didn't mention anything about weight. Maybe mh's are a specail breed when it comes to weight, air pressures, handling. Thanks again for the post.
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Old 08-28-2009, 09:34 PM   #21
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Great sight it answers a lot of questions. Thanks
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Old 08-28-2009, 09:43 PM   #22
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I understand tires are to be inflated for the load and when cold. Still have a question if someone can answer it.
My RV is parked with one side in the morning sun just before leaving on my trip. I check the tire pressure and find that the tire in the sun is maybe 5 psi more than the tire that is still in the shade. What do I do?

And don't say get up before sunrise to check tires!!
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Old 08-28-2009, 10:49 PM   #23
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I have a Pressure Pro and I see 5 lbs difference on the sun side to the shade side. Running I see 10 lbs or more. The Presure Pro is well worth the money, but use steel value stems.
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Old 08-29-2009, 07:11 AM   #24
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"To the poster regarding presures increasing 5-10 lbs when ambeint temp goes from 55-90 is hard for me to believe. "



Sorry Elkhart.... posted wrong quote last time.

Was just trying to point out that tire pressures do increase psi significantly as ambient temps rize. Set your pressures in the morning when the tires are cold and you are good to go.
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Old 08-29-2009, 06:24 PM   #25
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Always check your tires when they are cold and haven’t been driven more than one mile. The load capacity for a given cold inflation pressure is based on ambient outside temperatures.

The pressure in a hot tire may be as much as 10 to 15 psi higher than the cold tire pressure, therefore you will only get an accurate reading when you check your RV tires when they’re cold.

Air temperature and atmospheric pressure have an effect on tire inflation.
If the temperature increases 10 F, tire inflation increases 2%. If the temperature outside drops 10 F, the inflation pressure in your tires will decrease 2%.

When it comes to atmospheric pressure, the psi increases .48 psi for every 1,000 feet increase in altitude. And conversely, the psi decreases .48 psi for every 1,000 foot decrease in altitude.

If there are temperature and altitude changes when you’re taking your RV on a trip, it’s important to check your tire inflation more frequently.
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Old 08-29-2009, 06:32 PM   #26
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I understand tires are to be inflated for the load and when cold. Still have a question if someone can answer it.
My RV is parked with one side in the morning sun just before leaving on my trip. I check the tire pressure and find that the tire in the sun is maybe 5 psi more than the tire that is still in the shade. What do I do?

And don't say get up before sunrise to check tires!!
C'mon guys. I can't be the only one of us with this issue.
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Old 08-29-2009, 06:47 PM   #27
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If the sunny side reads 5 lbs more then simply make sure they are all equal on that side. Check them again when the sun isnt shining to make sure both sides are equal.
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Old 08-29-2009, 06:49 PM   #28
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Kix, I think you have already answered your question. Check and inflate them either in the sun, or darkness, so long as the ambient temp is the same from side to side. I would either check them the night before, given your parking situation, or before sunrise.


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