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Old 03-06-2014, 01:00 PM   #21
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In the car world I come from, tires are regularly delivered from the factory 10 and 15 PSI overinflated. Helps with two things, makes sure the car hits the dealer with enough pressure no matter how long it was stored and it helps prevent flat spots on the tires from storage.

Wouldn't surprise me if the same thing happens in the RV world and they might have missed checking the pressure.

And gauges do fail, my Snap On stick gauge failed on me when I was topping my TT tires up to trade it. Read 75 on one check, shot to 120 the next. Kept happening so I had to toss it. And I liked that gauge too, I had it for 15 years.
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Old 03-06-2014, 01:16 PM   #22
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YES! When we leave in April from MN and head south, I leave with 56 lbs of air in my D rated tires. By the time I get to Missouri, I have to start letting out air. (Yes, cold tires).

As an aside, my trailer originally came with C rated tires. My rims are only good for 60 psi. Since I'm way over on capacity, I don't worry about running 56 lbs cold. Just trying to keep everything within tolerances.
Had (TPMS) on last unit,very touchy reading,all Temp & Press OK in AM when leaving. Headed South,at 11 am SUN side Temp & Press UP! Same thing when Sun went to other side. I am NOT going to (Let Air Out) from side to side on a Trip? Youroo!!
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Old 03-06-2014, 01:20 PM   #23
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Originally Posted by youroo View Post
Had (TPMS) on last unit,very touchy reading,all Temp & Press OK in AM when leaving. Headed South,at 11 am SUN side Temp & Press UP! Same thing when Sun went to other side. I am NOT going to (Let Air Out) from side to side on a Trip? Youroo!!
This is the main advantage of Nitrogen filled tires, constant pressure no matter the temp.
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Old 03-06-2014, 01:30 PM   #24
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This is the main advantage of Nitrogen filled tires, constant pressure no matter the temp.
My last camper had the sticker denoting nitrogen filled (bought new) and I still had some variation in pressures with temp changes. Maybe less than with compressed air???
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Old 03-06-2014, 01:49 PM   #25
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Physics still apply, but with N2 it's a far smaller change, usually less than a pound with typical temps. Now, if you're reading 79.5 and it rises .6 psi you'll still see a change from 79 to 80.

But if you were seeing a large swing, two or three psi, then odds are there wasn't N2 in there. Shop air and likely moist shop air to boot.
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Old 03-06-2014, 02:34 PM   #26
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Physics still apply, but with N2 it's a far smaller change, usually less than a pound with typical temps. Now, if you're reading 79.5 and it rises .6 psi you'll still see a change from 79 to 80.

But if you were seeing a large swing, two or three psi, then odds are there wasn't N2 in there. Shop air and likely moist shop air to boot.
I would see several PSI change in mine. I might be at 62 PSI on a cold morning, say 25 degrees, but then be at 70 PSI while towing that afternoon with temps at 70 degrees, for example.
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Old 03-06-2014, 09:20 PM   #27
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I would see several PSI change in mine. I might be at 62 PSI on a cold morning, say 25 degrees, but then be at 70 PSI while towing that afternoon with temps at 70 degrees, for example.
Rule of thumb is 1PSI for every 10* change in temperature, for properly dried shop air. So you were seeing probably 100* at the tires, which I would consider consistent in 70* weather. So I sincerely doubt you have purified N2 in your tires.

Whomever installed the N2 should be able to check it and then exchange it back at no charge, that's usual.
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Old 03-07-2014, 09:03 PM   #28
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Do a search online for a tire size/load /pressure required.I replaced my c rated with e rated tires for safety,Maxxis tires has a chart and for my 8,000 lb axles I run 65 PS I for that maximum load rating and not the 80 PS I max rating.Not a problem,tire temps are low with excellent wear pattern. The chart will help you understand the pressure requirements-
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Old 03-08-2014, 07:44 AM   #29
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I always go by the placard, on my cars and TT. It takes into account the weight of the vehicle to give you a psi for the optimum footprint of the tire contacting the road. If you overinflate, the full width of the tread will not be in contact with the road. The tire will wear more in the middle, and there will be less tread area supporting the weight of the TT.

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Old 03-08-2014, 09:08 AM   #30
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Auto/truck makers set pressure based upon load not the max for the rated tire.TT makers always set standard to max tire rating,its just the way they do it to cover their butts for overload.I suspect some blowout issues are caused by over inflation etc.I found the standard inflation load/size/pressure table used by the tire manufactures.lets use my tt trailer size of st225x75r15.The C rated tire will carry the following loads/pressure.psi/load=40/1880,45/2020,50/2150 (max pressure), the same E rated tire psi/load= 55/2270,60/2380,65/2540,70/2620,75/2720,80/2830(max load.I use E rated with 8,000 lb axles set COLD at 60-65 psi. THESE PRESSURES ARE THE DOT GUIDLINES USED BY ALL MANUFACTURES TO SET LOAD RANGE RATINGS.Also,they fit the same rims as my C tires did and carry better load within the pressure rating of the rim which is 60 psi cold with a 10 % heat adjustment.
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Old 03-09-2014, 07:17 AM   #31
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Everyone great information and I appreciate all of the replies. I am going to change the air pressure setting from 58psi to 50 as this is what the max rated air pressure setting says on the DOT sticker on the side of the TT.
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Old 03-09-2014, 08:21 AM   #32
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Dont be confused by the DOT sticker.It is affixed as required by law but the DOT does not determine the psi/load ratings,the builder does.If anyone has a trailer,5th wheel etc with a dot sticker showing a psi rating less than max sound off.You will not find one,they all set the max tire psi rating without regard for the weight.The big reason is because they install marginal tires for the weight from the factory.
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Old 03-09-2014, 10:53 AM   #33
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One of the DOT regulations the RV trailer manufacturer must comply with during tire fitment instructs them to provide tires capable of supporting the maximum load of the axles GAWR and establish the recommended cold tire pressures for those tires. It’s a minimum requirement. Now days most RV trailer manufacturers provide OE tires with some load capacity reserves. It’s a good thing as long as you air the tires to the vehicle manufacturer’s recommendations.

ST tire manufacturers tout them as being able to operate at their maximum allowed tire pressures at all times.

Decreasing tire pressure increases sidewall flex. The ST tire will then build up more heat thus shortening it’s life expectancy.

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Old 03-09-2014, 11:34 AM   #34
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Originally Posted by Airdale View Post
One of the DOT regulations the RV trailer manufacturer must comply with during tire fitment instructs them to provide tires capable of supporting the maximum load of the axles GAWR and establish the recommended cold tire pressures for those tires. It’s a minimum requirement. Now days most RV trailer manufacturers provide OE tires with some load capacity reserves. It’s a good thing as long as you air the tires to the vehicle manufacturer’s recommendations.

ST tire manufacturers tout them as being able to operate at their maximum allowed tire pressures at all times.

Decreasing tire pressure increases sidewall flex. The ST tire will then build up more heat thus shortening it’s life expectancy.

Airdale
SO going from 58psi to 50psi, which is the max tire pressure rating on the sidewall of the tire and the DOT sticker, is the right thing to do. Thanks again everyone....
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Old 03-09-2014, 02:18 PM   #35
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All St tires are made in China,so don't believe what they tell you.The maximum side wall stamping is exactly that, maximum.The load charts are readily available from Goodyear,Firestone and many others including Maxxis ( one of the better China bombs.Tire pressure and load must be used to determine the proper pressure. I run a race car using several brands of tires and have discussed this issue with tire engineers because we run our 28 ft car carriers with St tires and we set pressure based upon load as they recommend. But,to each his own ,but I solved my tire problems using the load tables as recommended.
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Old 03-09-2014, 07:20 PM   #36
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Originally Posted by keypunch View Post
All St tires are made in China,so don't believe what they tell you.The maximum side wall stamping is exactly that, maximum.The load charts are readily available from Goodyear,Firestone and many others including Maxxis ( one of the better China bombs.Tire pressure and load must be used to determine the proper pressure. I run a race car using several brands of tires and have discussed this issue with tire engineers because we run our 28 ft car carriers with St tires and we set pressure based upon load as they recommend. But,to each his own ,but I solved my tire problems using the load tables as recommended.
Tire load inflation charts are developed by the Tire & Rim Association in corporation with its members - tire manufacturers. Without standardization vehicle manufacturers wouldn’t have any guidelines for tire load and inflation information. They were never intended for use by the private sector of the automotive or RV trailer family of tires. All of those tires are regulated by the industry that builds them in accordance with the various FMCSA safety regulations. Those regulations require the vehicle manufacturers to select the appropriate tires for each of the vehicle’s GAWRs and then set the recommended tire pressures. You will not find any documentation that recommends using lower recommended tire pressures for any of the above vehicles other than what is displayed on their federal certification label, tire placard and the vehicle’s owners manual. There may be special circumstances that will be found in the vehicle’s owners manual.

The popular Maxxis M8008 is manufactured in Taiwan. Thailand, Vietnam, Korea also manufacture ST. The best way to verify a tire’s country of origin is to get the codes from each individual tire and find them in the list for tire plant codes. Here is the reference.

http://www.harriger.com/tires.htm

Airdale

p.s. Tire pressures for the automotive industry are not comparable with RV trailer industry. They are set differently by their manufacturers.
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Old 03-09-2014, 09:40 PM   #37
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This will be my last post on this subject.The charts I use and referenced are for ST rated tires.Will not post them all ,just MAXXIS.Should mention that most of their tires are made in China and as I said earlier they are one of the better ST tires.Be informed and make your own decisions.Walk an rv lot and every trailer with a specfic load range tire will all use the max psi without consideration for any weight differences.ie all C range will show a placard of 50 psi.Visit their web site as the chart is difficult to post.


Maxxis trailer tires combine rugged durability and advanced construction for a smooth, comfortable ride. That’s why Maxxis is the choice of so many cargo and travel trailer manufacturers. For load/inflation info on Maxxis’ trailer tires, check out the chart below.
LOAD/INFLATION INFORMATION FOR ST METRIC TRAILER TIRES

TIRE LOAD LIMITS (LBS) AT VARIOUS COLD INFLATION PRESSURES (PSI)
FOR ST TRAILER TIRES USED IN NORMAL HIGHWAY SERVICE
Tire SizeMax Speed
Rating (MPH)Inflation Pressure - PSI253035404550556065707580ST205 / 75R1465117013001430(B)153016401760
(C)ST205 / 75R1565122013601480(B)161017201820(C)194020402150
(D)ST215/75R1465127014101520(B)166017901870
(C)ST225/75R1565143016001760(B)188020202150(C)227023802540( D)262027202830
(E)ST175/80R136590510001100(B)119012701360
(C)ST185/80R136599011001200(B)130014001480
(C)ST235/80R1665172019202090(B)227024302600(C)273028703000( D)313032603420(E)



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Old 03-09-2014, 10:06 PM   #38
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Tire manufacturers DO NOT set recommended tire pressures. Vehicle manufacturers do.

My posts are factual and based on tire industry standards and DOT regulations.

Here is an example of how tire industry standards are used. Read carefully. It supports what I have already written.

http://www.trucktires.com/bridgeston.../WeighForm.pdf
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Old 03-10-2014, 06:28 AM   #39
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Originally Posted by Airdale View Post
Tire manufacturers DO NOT set recommended tire pressures. Vehicle manufacturers do.

My posts are factual and based on tire industry standards and DOT regulations.

Here is an example of how tire industry standards are used. Read carefully. It supports what I have already written.

http://www.trucktires.com/bridgeston.../WeighForm.pdf

TRUE "Tire manufacturers DO NOT set recommended tire pressures. Vehicle manufacturers do."

At the end of day my questions was around experience with the West Lake Tires and why they might be inflated to above the stated max air pressure. Not sure we ever really answered that. Some gave great opinions on the matter, but ultimately the right thing is to never exceed the max rated amount.

Yesterday I set them at 50psi and I hope the tires give a good useful life.

thanks,
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Old 03-10-2014, 07:31 AM   #40
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Had (TPMS) on last unit,very touchy reading,all Temp & Press OK in AM when leaving. Headed South,at 11 am SUN side Temp & Press UP! Same thing when Sun went to other side. I am NOT going to (Let Air Out) from side to side on a Trip? Youroo!!
X2 Gary, I very meticulously set mine @ 65psi @ 40° and within 30 minutes they gained 5# on the sun side and about 3 on the shade side. While in FL and the temp dropped to 29°, they were reading between 57 & 59. As soon as the temp got back to 40, they were back reading between 63-65 depending on the sun. As a rule of thumb, NEVER DEFLATE A WARM TIRE & ALWAYS CHECK THEM IN THE MORNING BEFORE MOVING.

BTW, I am going to get the 'flow thru' monitors as the ones I have are a PITA to get the pressure correct.
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