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Old 12-01-2006, 12:32 AM   #29
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2 clarifications regarding my last post...

d rated marathons are rated to 2540 lbs...
at 80% load (2030 lbs) 45 psi is the recommended inflation,
so one would inflate to 55 psi and still be under max inflation...
IF wanting to travel at 65-75 mph

the goodyear care guideline...
"based on industry standards, if tires with the ST designation are used at speeds between 66 mph and 75 mph,
it is necessary to increase cold inflation pressures by 10 psi above the rocommended 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."


my unit 3 axle 11,500 lbs gwr....6 tires d rated to 15,000 lbs

properly loaded to the max of 11,500 lbs the tires are at 75% capacity,
so from the inflation tables 40-45 psi is recommended.....at 65mph and 55psi at 75 mph.

and as i often carry/travel at 10,500 lbs...
the tires are at less than 70% max capacity...1700 lbs each.
so the recommended pressures go down to 35 psi!!! and at higher speeds add 10psi to 45...
still very soft.

a doube axle 30/31 is an entirely differnt critter....gwr 10,300 lbs. on tires rated to 2540x4=10,160 lbs.....nearly maxed out! so recommended pressures are 65 psi which is also maximum inflation pressure...

could it be that the heavier dual axle trailers max out and stress out the marathons moreso than other models? and that some of these tires are underinflated, over load....and exceeding 65mph?

on what size/load rated trailers are tire failures reports?

does anyone understand this post?

cheerrs
2ari'
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Old 12-01-2006, 05:58 AM   #30
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My opinion is that you should run them at 65 PSI no matter what load you are carrying. That is what I run mine at. I think that running them below max tire pressure causes the failures. But that is just my opinion. I run all my trailer tires, (I have 4 trailers) at their max pressure and have only had one flat in the last 20 years. It was on a Marathon and I had run over a 1/4-20 bolt in the driveway.
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Old 12-01-2006, 06:52 AM   #31
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Hi 2air; I believe that you have nailed it down to the source of the problem. If you are late for very important corporate meeting, leave your As parked.
With the TV rating capacity and running gear maxed out, why would one want to travel at 85 mph? You're vacationing aren't you? Don't you want to enjoy the scenery instead of developing white knuckles?
I am glad that you have brought to attention the tire inflation logic.
Most, will inflate the tires to max pressure, needed or not. Often we see 3500 lbs boat traiers with dual axle and D tires inflated to 65 PSI. Result, sheared bolts, loose windshields and stressed out trailer frames from vibration. Heavy sidewall tires such as D and E rated tires having more rubber retain heat more so than lower rated tires. As you have pointed out it is very important to adjust the inflation rate to the weight they need to carry. Over inflating the tire, stresses the integrity of cordage especially when exposed to high heat factor. Towing a 42' Fountain weighing 11000 lbs on a tri axle with ST225/75D15 radials for past two years, each 2450 lbs capacity tire carries 1833 lbs at 50 lbs with no ill effects. It should be said here as well, that winding roads do have a considerable affect on tri axles in build up of heat.
It is very possible that the failures are tied exactly to what you have pointed out. Good post 2air. Thanks "Boatdoc"
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Old 12-01-2006, 06:55 AM   #32
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I've followed the rule Pick is talking about for the past 4 Airstreaming years. I check them before I go, while in transit and same on the return trip. Clearly my loaded Safari at 6300lbs GVWR won't even come close to the max rating, yet I guess I too like Pick am old school figuring that less pressure equals a bit more friction, causing a bit more heat. I think we all have the same tires from the factory no matter what size trailer, even up to the 34' units...those just get another axle, but two more of the same tires.....

It is however good information to know about the speed, PSI info.
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Old 12-01-2006, 01:43 PM   #33
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hi rubber heads...

well my point was/is the speed ratings mean different things for ST versus passenger tires.

visit the goodyear website www.goodyear.com

then click on north america, rv/trailer tires, and

then on the 'rv/trailer tires guide'...

in pdf format; takes a few seconds to download the entire pdf document.
it is worth it....copy and save for future use.

here is the link....

http://www.goodyear.com/rv/pdf/rvbrochure.pdf

marathon info on pages 9 and 16...



we do all get the 'same tires from the factory' but not all the same size or load rating....

big difference between the 'c' rated and 'd' rated for loads and inflations...

the c rated tires max out at 50 psi... and not all units use 15 inch size.

i realize that most failures or premature decline are related to UNDER inflation.

as boatdoc notes inflations way above what the load dictates...increase vibration related wear for the trailer.

so there is plenty of logic in using the 'load-recommended inflation' guide goodyear provides....on page 16.

gotta weight it, gotta measure inflation, gotta add/substract air....

the guideline also specifies what to do "between 66 and 75 mph"

and how air temps affect working inflation pressures.....

since i travel at 72 mph i do run at 65 psi most of the time....

but IF i were in 100 degree temps and only at 50-75% of the tire load rating....

i'd consider using the cold inflation guidelines and start the day at 45 psi...
and travel slower.

anyone with a trailer that maxes out the tire load rating has less margin for everything...speed, load, temp, wear, balance and so on...

and all of this requires a recent weight in for the trailer....which most do not do...

cheers
2air'
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Old 12-01-2006, 07:04 PM   #34
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Goodyear Marathon Failures

To answer a question from Dave in Elgin,
Walker Tire was not the dealer. The Goodyear dealer was one called Goodyear Auto Service Center. I'd rather not say which one.

Dave, you sure have a good looking Airstream. If you have any interest in joining our local group of Airstream owners, we are called the Texas Highland Lakes Unit of WBCCI. Our webb site is:
www.wbregion9.org/txhlunit.html

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Old 12-01-2006, 08:20 PM   #35
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Quote:
Originally Posted by 2airishuman
2 clarifications regarding my last post...

the goodyear care guideline...

does anyone understand this post?

cheerrs
2ari'
Ow! My head hurts.
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Old 12-01-2006, 09:44 PM   #36
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Mine too!
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Old 12-01-2006, 09:48 PM   #37
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Interesting complaint/ all the answers

Quote:
Originally Posted by Silvertwinkie
You know, the more and more I think about this, the more puzzling I find it. In one hand, you have what I would consider a fair number of people having issues. Statistically small given the number of tires out there, but concerning nonetheless. OTOH, there are folks like me that may just be lucky. I check the pressures all the time, load carefully and my Safari is nowhere near the max weight rating of the tires combined.

Then I read about speeds, weight distribution of load, etc and can't help but wonder if some folks that have had issues (not all) simply don't check the pressures and drive faster than 65, regadless of outside temps.
Well, after another dozen or so posts, Silvertwinkie, I agree with your thoughts. I'll go a step further. In 1999, I had a blowout on a 1996 30' Excella. I do meticulously maintain my tires. I do not drop the air pressure way down as I know the only drawbacks of keeping high pressures are slightly stiffer rides, and possibly accelerated wear in the center.
All I did was call the customer service 1-800 number, and very calmly and maturely told them what happened. I had the dates of the tires, the tread remaining, the trailer weight and GVWR, the size Marathons, and the specifications.
They didn't give me the third degree. They didn't hassle me or ask for proof of my checking pressures. They paid to have the blown tire shipped to them. They got back to me within 3 days. However, I must give Goodyear a lot of accolades. They GAVE me 4 new tires, and paid to fix the side of my trailer (ripped skirt in front of the tire) 15 minutes on the phone and a couple of hours at the Goodyear dealer, and I was very pleased-both with Goodyear and what they did.
Yes, I still run Marathons, have been many thousands of miles on them, and with that one exception, have never had any trouble with them. I think that 85% fact may be so very real. I change my tires every 5 years.
By the way, with so many members of this forum and so many tires amongst us, how many posters have had problems?
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Old 12-01-2006, 09:58 PM   #38
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the goodyear care guideline...
"based on industry standards, if tires with the ST designation are used at speeds between 66 mph and 75 mph,
it is necessary to increase cold inflation pressures by 10 psi above the rocommended 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."


cheerrs
2ari'[/quote]


2air ,
If I am reading this last sentence correctly , Goodyear is saying that IF the wheel is strong enough and IF you want to drive at speeds from 66-75 mph , that on a D rated ST tire you can inflate the tire an additinal 10psi beyond the 65psi stated on the sidewall for max load .
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Old 12-01-2006, 10:09 PM   #39
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Quote:
Originally Posted by ticki2
2air , If I am reading this last sentence correctly , Goodyear is saying that IF the wheel is strong enough and IF you want to drive at speeds from 66-75 mph , that on a D rated ST tire you can inflate the tire an additinal 10psi beyond the 65psi stated on the sidewall for max load .
hi tickl2...

yea that is confusing...

close but what it says is 10psi above the 'recommended' inflation for the load...and not over the wheel rating, and not more than 10 psi above the recommended pressure for the load....

in another place it notes not over the max cold inflation printed on the side walll (50 or 65)

visit the pdf guideline for the complete goodyear info...

i can't cut/paste from the pdf for some reason....

cheers
2air'
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Old 12-02-2006, 05:25 AM   #40
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It Blows me Away..........

How that some people can NEVER, EVER, read a single word from tire guidelines, then check their tires once or twice a year, run the tires at 75-80 (yes, that is real too) for 7-8 years and never have a problem. That just goes to prove that the more that you know can go wrong, the more that will!
We all need to quit educating ourselves.
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Old 12-02-2006, 07:35 AM   #41
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I understand that the key to proper inflation is getting the actual trailer weight.

after getting that following the guidelines for inflation at that weight see chart

TIRE LOAD LIMITS (LBS) AT VARIOUS COLD INFLATION PRESSURES (PSI) HIGHWAY STEER AND ALL POSITION TREAD
DESIGNS USED IN NORMAL HIGHWAY SERVICE*
LOAD/INFLATION INFORMATION FOR RV ST METRIC TIRES
Max Speed Tire Rating Inflation Pressure - PSI

...................... 15 ...20 ...25 .....30... 35...... 40 ...45 ......50 ......55 ....60 ...65

ST205/75R15 65 905 .1070 1220 .1360 1480(B) 1610 1720 1820(C)
ST225/75R15 65 1060 1260 1430 1600 1760 .....1880 2020 2150(C) 2270 2380 2540(D)

So if you wanted to carry 8000 lbs over 4 tires 45psi would do it (in red)

now if you want to go over 65mph inflate to 55psi.

I think that's what this all means????


Another interesting thing I see in that pdf is the LT tires don't carry as much load as the ST's
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Old 12-02-2006, 11:56 AM   #42
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Quote:
Originally Posted by Lipets
So if you wanted to carry 8000 lbs over 4 tires 45psi would do it (in red)
now if you want to go over 65mph inflate to 55psi.
I think that's what this all means????
Another interesting thing I see in that pdf is the LT tires don't carry as much load as the ST's

exactly right lipets....and not that complicated either!

cheers
2air'

denellen was just joking in his post...he drives old mgs which run on solid rubber tires or wagon wheels...

he and i will sort this out over a big bottle of vino, in florida...you are invited to join us.
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