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Old 12-15-2013, 10:42 PM   #1
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what pressure for a "tired head"

Some one a while ago said all this discussion gave him a tired head and I fully understand.
I did however side with what I think is the conservative and safe side of the discussion and recently ordered a full set of Sendel T03 and Michelin LTX M/S2 LT 225/75R16 to be delivered around Christmas.
I will put them on my 2010 25 FB FC whose book GVWR is 7300.
this is my seventh trailer since 1974, my first Airstream and perhaps my fifth set of tires for various trailers. I do not load my trailer heavy of this I am certain.
I have experienced catastrophic GYM failure on two tires with previous trailers neither of which cased damage to my trailer. Both failures were while wintering in Arizona and running on Interstate Highways. I have had good experience with 15" Carlise but all that is now beside the point. I have made the decision to go with the 16" wheels and feel very comfortable with it.
My question is what is the best pressure to run this new system at?
I've read the pros and cons of manuf recommendation vs something less for trailers of my weight but where should I start? Intuitively I suspect it should be less than the maximum but how much less?

I appreciate experienced advice on this issue.

Lou
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Old 12-16-2013, 06:32 AM   #2
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70psi.
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Old 12-16-2013, 09:12 AM   #3
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Know your trailer weight while loaded for over the road and open this chart up and check the correct pressure for that load.

The chart is a Goodyear chart but the Federals require all tires of a given size meet the same standards.

http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

Most trailers are running down the road will overinflated tires based on the MAX weight on the sidewalls.
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Old 12-16-2013, 09:14 AM   #4
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Check your tires before installation for these Michelin tire recall dates where there could potentially be a defect:

LT225/75 R16 115/112R LRE Michelin LTX M/S
DOT TIN B3JHAKEX and DOT date range 0210 thru 2512

I installed the Michelin LTX (P) 235/75R15 XL tires on my 2013 International Serenity 25FB with good results and based upon our experience fully loaded for camping (trailer alone was a 6,960 pounds including about a 1,100 pound tongue weight as the axles were supporting 5,880 pounds) had about a 22% safety margin above the derated capacity of 1,983 pounds per tire. The suggested tire pressure for these tires was 44 psi which gave the trailer a softer ride than the GYM tires at 65 psi.

Check out the photo of the GYM takeoff (just after getting the trailer home from the selling dealership so total miles from the factory to that point were about 2,500 miles) beside one of the new Michelin tires. Both were mounted on a factory rim. Click on the word "images" below my avatar.

The 16" tires are only 0.3" taller than the 15" Michelins with the total loft to the trailer of just under 0.5" over the GYM tires.

Per the 16" Load E Michelin specifications:

80psi 2,680 (E)
75psi 2,560
70psi 2,440
65psi 2,335 (D)
60psi 2,190
55psi 2,060
50psi 1,940 (C)
45psi 1,790

I would suggest installing a TPMS to monitor tire temps and pressures to find the best pressure for your setup. I ordered the Dill 1503-453 TPMS system tailored to the Airstream.

One can have too much load capacity tires and if they are deflated to a lower pressure for the much lower load, the stiffness in the sidewalls could be reduced to the point of possibly scrubbing a tire off the rim in a very tight turn.
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Old 12-16-2013, 09:32 AM   #5
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Switz,
Are you going with the Michelin LTX (P) 235/75R15 XL tires on your 2014 Classic?
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Old 12-16-2013, 10:27 AM   #6
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I run 70 psi on my 28ft international with good results.
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Old 12-16-2013, 04:12 PM   #7
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I run 70 PSI on my Classic 28. Gross weight 8800#, but I always run much lighter than that. Except for passing, I stay at 65 mph or lower. No visual wear in one year of tire use.
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Old 12-16-2013, 05:33 PM   #8
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tired head and pressure

Thanks for the input. I think 70 is a good place to start and then carefully monitor pressures and heat. My wife believes I'm paranoid about tires but I will do anything reasonable to avoid tearing up my airstream or compromising our safety.

I have worn Michelins on my cars and trucks for forty years and have never had a tire issue beyond nails and screws. I replace them well before they get to the wear lines.

this forum is great and I read it every day and contribute from time to time.

thanks to all.

Lou
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Old 12-16-2013, 06:19 PM   #9
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Quote:
Originally Posted by campin hound View Post
Some one a while ago said all this discussion gave him a tired head and I fully understand.
I did however side with what I think is the conservative and safe side of the discussion and recently ordered a full set of Sendel T03 and Michelin LTX M/S2 LT 225/75R16 to be delivered around Christmas.
I will put them on my 2010 25 FB FC whose book GVWR is 7300.
this is my seventh trailer since 1974, my first Airstream and perhaps my fifth set of tires for various trailers. I do not load my trailer heavy of this I am certain.
I have experienced catastrophic GYM failure on two tires with previous trailers neither of which cased damage to my trailer. Both failures were while wintering in Arizona and running on Interstate Highways. I have had good experience with 15" Carlise but all that is now beside the point. I have made the decision to go with the 16" wheels and feel very comfortable with it.
My question is what is the best pressure to run this new system at?
I've read the pros and cons of manuf recommendation vs something less for trailers of my weight but where should I start? Intuitively I suspect it should be less than the maximum but how much less?

I appreciate experienced advice on this issue.

Lou
Somewhere on the left forward external portion of your trailer there is a federal certification label. With the 2010 model you may also have tire information in the form of a tire placard near your weight label. Both will display the vehicle's recommended tire pressure.

I can only give you my interpretation of how it's supposed to be done.

When plus sizing your trailer tires the obvious obstacles are wheelwell and axle spacing clearances along with the proper offset for your new rims. The recommended tire pressure (s) for your Original Equipment (OE) tires was set by the vehicle manufacturer. Because ST tires were the vehicle manufacturers selection the recommended tire pressures are based on that tire design. With ST tires 99% of the time you're going to find them set at full sidewall pressures. Mostly because the tire manufacturers wholeheartedly recommend full sidewall pressures for the ST tires and the trailer manufacturer doesn't want you to under pressurize them. .

The industry standards say the new recommended tire pressure for your plus sized tires must be set at the amount of pressure required to attain the load capacity provided by the OE tires at their recommended tire pressure. Deviations should be solicited from the vehicle manufacturer/tire manufacturer.

BA
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Old 12-17-2013, 06:55 AM   #10
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A word of caution about those tire load tables.

They are MAXIMUMS, NOT recommendations. The pressure listed is the absolute MINIMUM you should use. To get the usual reserve capacity (15%), you need to use 15 psi MORE than the minimum.

And don't forget to include the side to side and front to rear variation. All tires do not carry the same load - even if all 4 are very close together.
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Old 12-17-2013, 07:18 AM   #11
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Wink How tired is your head now?.....

"I will put them on my 2010 25 FB FC whose book GVWR is 7300.
this is my seventh trailer since 1974, my first Airstream and perhaps my fifth set of tires for various trailers. I do not load my trailer heavy of this I am certain."

Do not trust the 'book' values, go to the scales and find out for certain.

"I think I'll use this pressure because I think my trailer weighs this much" is not the best stragidy.


Bob
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Old 12-17-2013, 07:51 AM   #12
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The load capacity of the four 15" Michelins I used on the 25FB International was 7,970 pounds. That load capacity would not be adequate for the Classic model 30 with an factory literature empty weight heavier than the GVW of the 25FB.

Thus, to have enough load capacity to put stuff on and in the trailer, I would have to stay with the 2,540 pound rated Good Year Marathons or go to the 16" Michelins with a load capacity of 2,680 pounds. Since I installed 15" Michelins on the 25FB for safety, I will install the 16" Michelins on the Classic 30 for safety.

A local tire store said that since the recalled tires were the previous version of the Michelin LT225/75R16/E LTX M/S2 tires we have been discussing in all the tire upgrade threads (difference is LTX M/S in the designation), they might just upgrade those 1.3 million recalled tires to the new generation. That would put a bind on the supply of these tires for awhile. Thus I ordered mine yesterday while there is still some inventory. I had planned to order them in early January anyway.

Several folks have mentioned that 72 psi is a good starting point for the 16" Michelins. Then monitor tire pressures and temperatures while in use. That pressure would equal the 10,000 pound GVW of the Classic model 30.
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Old 12-17-2013, 03:22 PM   #13
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I've settled in at 75psi on my 30' Classic, after experimenting with 70, 75, and 80 psi.
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Old 12-17-2013, 08:30 PM   #14
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Has anyone checked the max PSI rating on the rims they are using?
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