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Old 07-08-2010, 06:43 AM   #15
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Have you noticed? It got hot this week. Obliquely speaking.
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Old 07-08-2010, 07:00 AM   #16
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I'm leaving today, ultimate destination in 3 days is "the mountains."
Should I prefill my tires with "mountain air"?
And where along I80 thru Illinois, Iowa, or Nebraska can I get some?
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Old 07-08-2010, 07:21 AM   #17
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This new tire table is pretty sharp just click your rim size and get prober inflation pressures.
Have found my tires after travel some distance will inflate an additional 10 to 15 lb's now thats allot of hot air.

This long article mention added 5 lb's "MH Tire Load & Inflation Ratings" but if you have any doubt's about proper inflation move to one block to right for your proper tire inflation in tables.
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Old 07-08-2010, 07:57 AM   #18
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007 I just looked at the Table you suggested. Is this statement in error? It is the last paragraph above the charts.

"In the load and inflation tables, SINGLE means an axle with one tire mounted on each end, while DUAL means an axle with two tires mounted on each end. The loads indicated represent the total weight of an axle end in an RV application. When one axle end weighs more than the other, use the heaviest of the two end weights to determine the unique tire pressure for all tires on the axle. The maximum cold air pressure for each axle may vary, depending on their weights. These tables are applicable for all RV axles, whether or not they are power-driven." Shouldn't this be Minimum? Never to exceed the Maximum? It is early in the morning for me. Am I missing something here? I have Goodyear tires and that chart only provides a PSI value for the weight. I am not familiar with this, Michelin, chart.
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Old 07-08-2010, 08:13 AM   #19
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Quote:
Originally Posted by two-niner View Post
I had just seen (on another forum)(which was taken down quickly) an old wives tale about tire inflation.
The gist of the matter was to inflate tires per manufacturers spec's, then add five (5) lbs. Personally I have never done that.
I am looking at Michelins RV Tires 32 page booklet. Nowhere do they say, state or intimate to add five pounds of air above their recommendation.
It is not an 'old wives tale'.... Goodyear does indeed recommend exceeding the max pressure on the tire under certain conditions for their Marathon trailer tire.

"IMPORTANT OPERATING INFORMATION
Industry standards dictate that tires with the ST (Special Trailer) designation are speed restricted to 65 mph under
normal inflation and load conditions, unless a different speed restriction is indicated on the sidewall of the tire.
Based on industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph, it is
necessary to increase the cold inflation pressures by 10 psi above the recommended pressure for the load.
Do not exceed the maximum pressure for the wheel.
If the maximum pressure for the wheel prohibits the increase of air pressure, then the maximum speed must be
restricted to 65 mph.
The cold inflation pressure must not exceed 10 psi beyond the inflation specified for the maximum load of the tire."

The above quote is contained on Pg 23 of the RV Brochure at the GoodYear web site under load info for the Marathon tire.

It does state 'do not exceed max pressure for the wheel', but I believe that they are referring to the wheel itself, not the tire.
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Old 07-08-2010, 08:26 AM   #20
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edj, I'd say is reading it right not MAX tire stamping on side wall but Max of your weight of load for proper tire inflation.
The article is what I was referring to about the 5 lb's.
Your Goodyear table may read inflations differently I would follow their advise for their tables.

Goodyear tire

Goodyear Tire table
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Old 07-08-2010, 08:48 AM   #21
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Quote:
Originally Posted by two-niner View Post
I had just seen (on another forum)(which was taken down quickly) an old wives tale about tire inflation.
The gist of the matter was to inflate tires per manufacturers spec's, then add five (5) lbs. Personally I have never done that.
I am looking at Michelins RV Tires 32 page booklet. Nowhere do they say, state or intimate to add five pounds of air above their recommendation.
It's time to put this chestnut to bed, at least for Michelins.
My old computer will freeze if I try to make a clicky but here it is:
www.michelinrvtires.com
Dag nag it, the clicky worked.

Kerry
I think that I'm following the same thread on the same forum. If so, I have the utmost respect for Brett Wolfe and the opinions that he offers.

When we first bought our RV, the old tires showed signs of heavy cracking in the side walls and we replaced all 6 within 30 days of our purchase. In the next 30 days, I had weighed the RV on a CAT scale with all tanks full (trying to simulate passenger weight) and taken it immediately to a Texas DPS truck enforcement site to have the 4 corners weighed. I used the Michelin table to determine my inflation pressures and added 5 pounds. My rational was simple. At that point, I didn't trust my brand new tire gauge to be accurate, even though it said that it was within 2%. Secondly, since I was well below the 110 lb maximum (I run 95lbs front, 90lbs rear) and above the recommended inflation pressures on the vehicle's sticker, I figured that I was in a safe range were I could experiment. The long term effect of slightly overinflated tires is more wear in the center of the tread than on the outside. In the 5 years that I kept those tires, I never saw that.

The other point not mentioned so far is ambient temperature. The tire makers have a specific ambient temperature as a baseline for their measurements. Here in Texas, we tend to run warmer temperatures. I figured that the extra 5 pounds of pressure in my tire gave me some safety margin for the temperature I have to deal with. To give you an example, we went to Yellowstone from Dallas. I set all of the tire pressures for the Dallas temperatures before we left. We drove the first day to Trinidad, CO and the next morning,those tire pressures held. The second day, we stopped in Casper, WY. The temps the next morning were 50 degrees cooler than when we started. and the tires were all significantly down in pressure. My 5 pound difference kept the tires in the pressure range for the load on the wheels.

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. I'm doing everything I can to keep it that way. The 5 pounds of additional pressure may indeed be an old wives' tale but I plan to continue it. I agree that isn't what the manufacturer has stated in writing.
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Old 07-08-2010, 09:04 AM   #22
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But... my old wife told me to add the extra 5lbs and I do what I'm told!
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Old 07-08-2010, 09:29 AM   #23
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Originally Posted by InPursuit View Post
KNOW your weight and calculate.
Folks, let's not propagate more tales. A resounding YES on know your weight and an absolutely NOT on calculate as in the given example. The inflation tables may not be linear (as per the calculation) and certainly DO have a minimum inflation for a given tire.

USE the tire manufacturers inflation tables for your specific tire and weight. There really is no other bona-fide choice and it really can't be any easier. Corner weights are best using the heaviest on an axle, or use axle weight divided in half and then always go to the table.
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Old 07-08-2010, 09:42 AM   #24
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Folks, let's not propagate more tales. A resounding YES on know your weight and an absolutely NOT on calculate as in the given example. The inflation tables may not be linear (as per the calculation) and certainly DO have a minimum inflation for a given tire.

USE the tire manufacturers inflation tables for your specific tire and weight. There really is no other bona-fide choice and it really can't be any easier. Corner weights are best using the heaviest on an axle, or use axle weight divided in half and then always go to the table.
Jeff is 100% correct.
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Old 07-08-2010, 10:04 AM   #25
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Might as well settle another tale. Cold Inflation temp.

Cold inflation temp means an UNDRIVEN tire at the AMBIENT temperature. So check in the morning for where you are located. Make sure the sun hasn't heated a tire too.

YES YES YES, if you drive from sunny Arizona to the frigid depths of Yellowstone (or vice verse) you WILL need to adjust your tire pressure as the ambient temp has changed. Same thing applies if you stay put in one location where winter vs summer temperatures change you should adjust tire pressure for seasonality too.

More debunking. 1) The cold inflation tables already account for the effects of tire heating as they are driven so never ever adjust pressure of a driven tire. 2) Furthermore the tables account for typical daily temperature swings as well so don't get all silly and adjust your tire pressure every time the thermometer changes over the course of a day. But if you change climactic location, change your tire pressure. 3) And yes, if you check your pressures in a heated garage and yet drive outside where the ambient is different, well, you'll need to park outside in order to check the pressure.
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Old 07-08-2010, 10:14 AM   #26
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No old wife here. I just took an easy practical approach to tire pressure.
1. I have stock tires.
2. I have no illusions about my F53 truck chassis riding like a Prevost
3. I always run close to but not over max weight.
4. The wall placard for the MH says 84 PSI
5. The tires say 95 PSI max

I split the difference and run 90 PSI this covers gauge calibration variances, minor elevation changes, and regional temperature changes. This may be a simplistic approach to tire psi but is perfectly safe and is one less thing I have to stress over so I can enjoy the use of my MH.
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Old 07-08-2010, 10:31 AM   #27
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Originally Posted by chasfm11 View Post
The other point not mentioned so far is ambient temperature. The tire makers have a specific ambient temperature as a baseline for their measurements. Here in Texas, we tend to run warmer temperatures. I figured that the extra 5 pounds of pressure in my tire gave me some safety margin for the temperature I have to deal with.
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.

Quote:
To give you an example, we went to Yellowstone from Dallas. I set all of the tire pressures for the Dallas temperatures before we left. We drove the first day to Trinidad, CO and the next morning,those tire pressures held. The second day, we stopped in Casper, WY. The temps the next morning were 50 degrees cooler than when we started. and the tires were all significantly down in pressure.
This is known as an anecdote. A thousand and one things (f'rinstance elevation changes) could be underlying the phenoma you describe occurring.

Quote:
My 5 pound difference kept the tires in the pressure range for the load on the wheels.
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.

[QUOTE]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.

Quote:
I'm doing everything I can to keep it that way.
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.
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Old 07-08-2010, 11:10 AM   #28
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Originally Posted by mudpuppy View Post
I wonder how many blowouts are due to under inflated tires by folks looking for a Cadillac ride from a truck chassis.


Right there is probably the BEST analysis on the issue in this whole belabored thread!

I swear - some RVers seem so fixated on tire PSI, they must stop at every 1000 foot change in elevation to adjust tire PSI - and again, the same if the ambient temp changes 5 degrees!

YUP, safety IS important - and yeah, damage from blown tires can be very expensive, but such paranoia over PSI must surely degrade the otherwise enjoyment of RV travels and the beauty of the passing landscape...

And no - you DON'T have to readjust tire PSI while parked in that park or CG, just because the barometer dropped 2 points...
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