Following the load/pressure chart for GY Endurance

[Markj55]

I agree with most everyone on this subject..... nothing to be gained by ‘low riding’ your AS. The thought of it evokes scary dreams, not to mention possible handling issues. It seems to me that wear to the outside portions of the tire would increase and over stability of the ride would decrease.

I run Michelin’s on my Tundra at 35-36psi front and 40psi rear and my GY Endurance at 65-70 psi on my 19’ depending on temperature. For me that has proven to be the sweet spot for overall ride and handling. After running them at 80psi for a few hundred miles I quickly found that to be a rough ride.

I’m curious if anyone has run their rig on 25psi and why?

[smithcreek]

Originally Posted by tlars

Do I really intend to run my tires at 25 psi? Absolutely!

The language of the table is confusing. It does NOT give recommended psi. What is does give you is a LOAD LIMIT for your tires at a given PSI. The tire experts on the forum generally advise running you tires as close to max sidewall pressure as possible and only decreasing if you feel it's too rough on the trailer. The recommended psi for my FC20 is 65, which happens to be the max sidewall pressure of the old Marathons. With the new GYE I run at 72. Much above that, drawers and cabinets start to open and stuff bounces out.

[CapriRacer]

That load table is a MINIMUM, not a recommendation.

The chart is supposed to be the STARTING point for setting tire pressures. In a perfect world, Airstream would take that chart, do some math, and come up with a pressure that is suitable and post in on the vehicle tire placard. We do not live in a perfect world and vehicle manufacturers learn through experience, and for trailer manufacturers, the world is still in a bit of a learning curve.

So here are my thoughts based on my experience as a tire engineer who called on a major car manufacturer.

As has been said above, the load on a tire varies from corner to corner. Unless you measure each corner, you can only estimate - and my estimate is that for trailers, the max load is at least 110% of the total for all 4.

For trailers, there is another factor that has been called "Tire Inter Ply Shear" and it occurs when a trailer is backed sharply into position. I don't think trailer manufacturers have a good handle on this yet.

Then there is normal good engineering practice. I had a college professor who called it "Overdesign / Underspecify!" - meaning as an engineer you should design a product to perform at more than the minimum, and you should specify those products to operate above the minimum. To me that means that tires should be specified at 115% of the rated load (or 85% depending on which way you want to look at it!)

I'm inclined to think that the engineers at Airstream are a whole lot smarter and know a whole lot more about their vehicle than I do, so whatever they specify on the vehicle tire placard is a whole lot closer to what I should be using, than the load chart starting point.

My experience tells me that any tire that experiences more than a 10% increase in operating pressure over the cold condition is being overloaded/underinflated. The would be my definition of "Underinflated".

[JohnandDonna]

Ah yes the great tire psi debate. I run between 70 and 75. 80 was just too rough. Dealer said 70-75 would be fine. 73 seems to be the sweet spot.

[tlars]

Thank you all for your input. There sure are many opinions out there. I went to two sources to get to the bottoms of this.
First the NHTSA National Highway Traffic Safety Administration. These are the guys that require trailer, car, etc. manufacturers to put the placards on the trailers. They also regulate what must be printed on them. Trailer manufacturers, as a group have decided to simply put the max PSI on the label. You can check this by walking through a trailer sales yard what's on the tire is on the label. Most of the regulation is in 49 CFR part 565 thru 575. It says you must put the Max PSI and max load unless you test and meet a whole bunch of requirements which I found to be dead end links. So I can not point to an exact regulation, it does seem logical that trailer manufactures simply took an easier way out and listed the max. Because of this they were required to put "see owners manual for further information".
So the Trailer Manufactures punted to the Tire manufactures. So off I went to Goodyear. Goodyear.com "contact us" has a chat function. It is intended to cover basic questions but they will reach out to experts if you encourage them to do so. Start off with a question like do you sell trailer tires. If you start off with a highly technical question, they will give you another phone number to call.
So my results: I told the chat person that I had 1375 lbs on each tire. Is it safe to run 30 psi in the Endurance ST225/75R15. The chat person said he had to check with someone. After a few minutes he came back and said it was OK. He also sent me a link to the chart. I have this transcript but Airforums blocked me from uploading it. I can email it to anyone interested.
I later realized that I did not ask for an exact PSI to run. So I started up the chat box again. I asked what PSI should I run with Endurance ........ It came back with call this number for technical assistance. It's the corporate office. 1(800) 782-7949. I asked my question to the technician. He quickly replied, (40psi) I asked why not 80? He said way way too rough. Keep in mind I have a 23fb flying cloud likely the lightest dual axle trailer Airstream makes. I then asked why not 30? He said no need, the tires will provide the cushion you need at 40 running them lower might get sloppy. I then told him that I was intending to report this information back to a group of airstreamers and gave him a chance to rephrase or check with his supervisor. He said the info is solid. But remind everyone that his recommendation is for 1375 per tire.
So sorry to put this to an end. simply call 1(800) 782-7949 and grill them all you want. My tires are at 40psi. I'm tempted to ride in it over a local rough road but I think it wil take Goodyears word for it. Thank you all!!

[tlars]

Originally Posted by CapriRacer

That load table is a MINIMUM, not a recommendation.

The chart is supposed to be the STARTING point for setting tire pressures. In a perfect world, Airstream would take that chart, do some math, and come up with a pressure that is suitable and post in on the vehicle tire placard. We do not live in a perfect world and vehicle manufacturers learn through experience, and for trailer manufacturers, the world is still in a bit of a learning curve.

So here are my thoughts based on my experience as a tire engineer who called on a major car manufacturer.

As has been said above, the load on a tire varies from corner to corner. Unless you measure each corner, you can only estimate - and my estimate is that for trailers, the max load is at least 110% of the total for all 4.

For trailers, there is another factor that has been called "Tire Inter Ply Shear" and it occurs when a trailer is backed sharply into position. I don't think trailer manufacturers have a good handle on this yet.

Then there is normal good engineering practice. I had a college professor who called it "Overdesign / Underspecify!" - meaning as an engineer you should design a product to perform at more than the minimum, and you should specify those products to operate above the minimum. To me that means that tires should be specified at 115% of the rated load (or 85% depending on which way you want to look at it!)

I'm inclined to think that the engineers at Airstream are a whole lot smarter and know a whole lot more about their vehicle than I do, so whatever they specify on the vehicle tire placard is a whole lot closer to what I should be using, than the load chart starting point.

My experience tells me that any tire that experiences more than a 10% increase in operating pressure over the cold condition is being overloaded/underinflated. The would be my definition of "Underinflated".

Good points...
Would you mind calling the technical information number at Goodyear (1 800 782 7949) and see if they have real technical expertise or just quoting off a info sheet.

[CapriRacer]

Originally Posted by tlars

Good points...
Would you mind calling the technical information number at Goodyear (1 800 782 7949) and see if they have real technical expertise or just quoting off a info sheet.

In my previous reincarnation, I was the guy those folks you called would contact to answer your question - but with another tire manufacturer - and No! They have NOT demonstrated any real technical expertise!

So before I go forward, I want to make sure you do NOT use 40 psi. Way, way too low!

My suggestion: Start with what is on the vehicle tire placard and the next time you tow, carefully measure the cold inflation right before you start, then measure the pressure buildup after an hour of Interstate driving. You shouldn't get more than 10% build up. On the other hand, 5% MIGHT indicate you are too high.

The reason I say MIGHT is because this is where MY expertise reaches the limit. I just don't have enough experience to say what is optimal.

[tlars]

Originally Posted by CapriRacer

In my previous reincarnation, I was the guy those folks you called would contact to answer your question - but with another tire manufacturer - and No! They have NOT demonstrated any real technical expertise!

So before I go forward, I want to make sure you do NOT use 40 psi. Way, way too low!

My suggestion: Start with what is on the vehicle tire placard and the next time you tow, carefully measure the cold inflation right before you start, then measure the pressure buildup after an hour of Interstate driving. You shouldn't get more than 10% build up. On the other hand, 5% MIGHT indicate you are too high.

The reason I say MIGHT is because this is where MY expertise reaches the limit. I just don't have enough experience to say what is optimal.

I'm new here so i'm not sure what all has been discussed so I will summarize what I have picked up from these threads. Please, anyone, correct me.
My largest complaint with my Airstream and what I believe is a major complaint with other owners is that the trailers seem to shake themselves apart. Rivets popping, floor separating from the frame, interior doors falling off, drawers not staying closed. My Flying Cloud 23fb weighs 5340lbs fully loaded. Four Endurance ST225/75R15 can support 11,320lbs at 80psi. I asked myself, why would I inflate my tires to the same pressure required for an 11,320 lb. trailer? So that is what sent me on this mission. I first went through the maze of the NHTSA regulations to find that the Trailer manufactures are allowed to put the max psi on the placard as long as they added "see owners manual for further details".
I then contacted Goodyear and was told that for less than half the load you need less than half the PSI (paraphrased) He actually told me 40PSI. That sure made sense.

A have to trust a company to properly manufacture there product , inspect it , test it's design and train their people to advise their customers. So I'm sticking with 40psi. Certainly when it makes sense. However I will contact Airstream and see if they realize that many of their customers believe they must inflate their tires to max load even when the actual load is a fraction of the max and in doing may be degrading the perceived quality of the Airstream product. And see what they have to say.

You will here from me if there is any problem running 40psi

[tlars]

Originally Posted by tlars

I'm new here so i'm not sure what all has been discussed so I will summarize what I have picked up from these threads. Please, anyone, correct me.
My largest complaint with my Airstream and what I believe is a major complaint with other owners is that the trailers seem to shake themselves apart. Rivets popping, floor separating from the frame, interior doors falling off, drawers not staying closed. My Flying Cloud 23fb weighs 5340lbs fully loaded. Four Endurance ST225/75R15 can support 11,320lbs at 80psi. I asked myself, why would I inflate my tires to the same pressure required for an 11,320 lb. trailer? So that is what sent me on this mission. I first went through the maze of the NHTSA regulations to find that the Trailer manufactures are allowed to put the max psi on the placard as long as they added "see owners manual for further details".
I then contacted Goodyear and was told that for less than half the load you need less than half the PSI (paraphrased) He actually told me 40PSI. That sure made sense.

A have to trust a company to properly manufacture there product , inspect it , test it's design and train their people to advise their customers. So I'm sticking with 40psi. Certainly when it makes sense. However I will contact Airstream and see if they realize that many of their customers believe they must inflate their tires to max load even when the actual load is a fraction of the max and in doing may be degrading the perceived quality of the Airstream product. And see what they have to say.

You will here from me if there is any problem running 40psi

I sent this info onto one of Airstream's regional sales directors. I'll forward any responce.

[Mike G]

The bottom line is that AS should not be putting 80# on the trailer placards. I doubt there's any science behind it, and I've never heard an explanation from them for it . . .

[Fair_Enough]

My 2 cents... I also have a 23FB with GYEs... GVW is 6000# , subtract tongue weight and there shouldn't be more than 5500# on 4 tires... divide that by 4 nets 1375# per tire, of course, the weight can't be perfectly shared by all 4 and I have no idea what actual tire weights would be. Going by the GY chart (it isn't generic, by the way) and following the 205Rx14 LR-D line to beyond that 1375# shows 35 psi will do it. With original 205x14 C-rated tires, AS recommended 50 psi, which is the max for most or all C-rated ST tires. I see no reason to inflate below 50 psi, but I have run them at 40 psi in the heat and tire temperature stayed well within a safe range. TP increased to 46 psi hot (based on TPMS), but could be higher on a hotter day. I inflate to 50 psi cold and it seems to me, my MPG is better there.
FE

[Mollysdad]

Originally Posted by uraljohn

Your trailer, your tires, your decision. As a couple other posts have requested let us know how 25 PSI works out. Maybe we are all wrong. Just sayin....

But the GoodYear engineers say it's the correct pressure. Who am I to disagree?

[tlars]

Originally Posted by Mike G

The bottom line is that AS should not be putting 80# on the trailer placards. I doubt there's any science behind it, and I've never heard an explanation from them for it . . .

Is not just AS, it's ALL trailers. Utility ,boat, RV etc. and it's all regulated and permitted by the National Highway Transportation Safety Administration. One major problem is that the placard looks just like the placard on cars and with cars you ARE to inflate your tires to the values stated. For trailers, it's the max air pressure not to be exceeded

By the way, AS has replied to my email as it continues to bounce around corporate offices and to my dealership RV One. No one has told to me to reinflate the tires back to 80 psi

[Bill M.]

"But the GoodYear engineers say it's the correct pressure. Who am I to disagree?"

You are, of course, just an average internet troll.

Thanks tiars, for posting your findings. I am going to look at it as a NTB created problem. The manufacturers seem to think they are safer to take the out of max pressure rather than to risk specifying something that probably takes too much testing. It does not seem like the NTB is willing to take the "chart" as real information.

[wulfraat]

Originally Posted by tlars;

....and with cars you ARE to inflate your tires to the values stated. For trailers, it's the max air pressure not to be exceeded

I don’t adhere to the inflation sticker on my 2500. The sticker is recommended tire pressure for GAWR. I vary the rear pressure between 55 and 70 depending on my bed load. I have an onboard air compressor for this reason.

If I ran at the “recommended” 75 in the rear with an empty bed I’d loose traction and wear out a center strip down the center of the tire due to over inflation.

I inflate base on load measured at cat scales along with my tire inflation charts for both TV and trailer, with some additional overhead added.

[Fair_Enough]

Originally Posted by tlars

I intend to follow the load /pressure chart with guidance from folks here...

... Trailer is a 2021 Flying cloud 23FB. Loaded weight connected to TV and hitch is 5340 lbs. GVWR is 6000lbs.

... I can add cushion to bring the trailer weight to 5500 lbs to load each tire at 1375lbs. So why don't I lower it further to 25psi??

First mistake is to expect a consensus concerning one of the topics some people get passion about.

What I will say is this, just between you and I, if you trust Goodyear by running them on your trailer, shouldn't you trust the chart they publish?

Or, should we trust Airstream that mindlessly shows the maximum sidewall tire pressure no matter the trailer or tire selected?

This to me is a "no brainer".

One other thing, I ask, what does your sticker show? Certainly not 80 psi? And, certainly your 23FB didn't come with E-rated tires. Yes... no?

My AS shows 50 psi on the white sticker, since it came with C-rated 14" Marathons. Which is actually too much air pressure. There isn't 1760# on each tire. The dealer installed new 14" GY Endurance D-rated when I bought it used. I don't know and don't care what they inflated to. I found the GY load chart and went by it.

Also my GY chart shows it takes 35 psi to cover that 1375 weight per tire (5500/4); not 25 psi. Shouldn't yours be the same? What we don't normally know is the actual weight per wheel location. They can't be identical. So, going up to 40 psi, IT SEEMS TO ME will cover any difference in loading... each tire then can carry 1530#. YMMV
FE

[tlars]

Originally Posted by Fair_Enough

First mistake is to expect a consensus concerning one of the topics some people get passion about.

What I will say is this, just between you and I, if you trust Goodyear by running them on your trailer, shouldn't you trust the chart they publish?

Or, should we trust Airstream that mindlessly shows the maximum sidewall tire pressure no matter the trailer or tire selected?

This to me is a "no brainer".

One other thing, I ask, what does your sticker show? Certainly not 80 psi? And, certainly your 23FB didn't come with E-rated tires. Yes... no?

My AS shows 50 psi on the white sticker, since it came with C-rated 14" Marathons. Which is actually too much air pressure. There isn't 1760# on each tire. The dealer installed new 14" GY Endurance D-rated when I bought it used. I don't know and don't care what they inflated to. I found the GY load chart and went by it.

Also my GY chart shows it takes 35 psi to cover that 1375 weight per tire (5500/4); not 25 psi. Shouldn't yours be the same? What we don't normally know is the actual weight per wheel location. They can't be identical. So, going up to 40 psi, IT SEEMS TO ME will cover any difference in loading... each tire then can carry 1530#. YMMV
FE

My 2021 flying cloud 23FB came with ST225/75R15 Goodyear endurance tires. The dealer inflated them to 80psi. The placard on my trailer says max load of 2830 per tire at max pressure 80psi.
I drove it home about 300 miles bone dry and the shelves in the pull out pantry had all fallen down, overhead compartments had opened up, cushions were all over the place.
On my second outing a larger Airstream parked next to me. i think it was an 25 or 27 foot international. I notice that it had the same tires as mine. His placard read exactly the same as mine. He ran 70 psi in his tires.
This is why I started this thread. The chart I refer to is a chart for Goodyear Endurance tires. Looking down an following the info for ST 225/75R15. After discussions with Good year, I now consider it as a minimum and the 80PSI the maximum. The advisor suggested 40psi which is about have way and I note that my load of 1375 is about half.

[CapriRacer]

May be it is time I explained where that chart comes from.

First, it is published by the Tire and Rim Association (TRA) - the tire standardizing body in the US. Goodyear merely reproduces it (with permission).

The chart is for tire manufacturers and vehicle manufacturers to design against. It was never intended to be a chart for end users - and it is certainly not a recommendation. It even says that the values are LIMITS!

In the case of tire manufacturers, they design tires to be able to EXCEED what is published there. The test is quite simple and involves a one hour sustained load at 100% of the rated load and rated pressure in a climate controlled room. That passes the government minimums.

This is where everyone seems to misunderstand the table. A tire built to consistently BARELY pass 100% of the rated load will frequently regularly FAIL in service. That's because the service conditions are not like the lab room - they are harsher. So tire manufacturers design their tires to EXCEED 100% - and by how much is a trade secret for each tire manufacturer and will vary depending on the type of tire. I think we can point to the Goodyear Marathon/Endurance as an example of how this is supposed to work.

In the case of vehicle manufacturers, it is a guide to help them get the correct tire size and inflation pressure. They also need to gain experience. A good example is the Ford Explorer. At the time (1996 to 2000) it was common for SUV manufacturers to specify their tire pressures such that the GAWR's and the max load for the tire size/inflation were the same. They no longer to that. The tire size/inflation are now at least 115%.

Trailer manufacturers (including Airstream) are still on their learning curve. It wasn't but 3 years ago that ST tires were routinely failing and there was a lot of gnashing of teeth over this. Fingers were pointed every which way.

Many trailer manufacturers responded by specifying the max pressure, that way they could never be blamed if the tire failed. I think all the trailer manufacturers are still sorting this out.

So how do we apply this to the OP's situation? In a day or so, I will take the info in the OP and show why the 40 psi value is wrong.

[smithcreek]

Originally Posted by CapriRacer

May be it is time I explained where that chart comes from.

First, it is published by the Tire and Rim Association (TRA) - the tire standardizing body in the US. Goodyear merely reproduces it (with permission).

The chart is for tire manufacturers and vehicle manufacturers to design against. It was never intended to be a chart for end users - and it is certainly not a recommendation. It even says that the values are LIMITS!

In the case of tire manufacturers, they design tires to be able to EXCEED what is published there. The test is quite simple and involves a one hour sustained load at 100% of the rated load and rated pressure in a climate controlled room. That passes the government minimums.

This is where everyone seems to misunderstand the table. A tire built to consistently BARELY pass 100% of the rated load will frequently regularly FAIL in service. That's because the service conditions are not like the lab room - they are harsher. So tire manufacturers design their tires to EXCEED 100% - and by how much is a trade secret for each tire manufacturer and will vary depending on the type of tire. I think we can point to the Goodyear Marathon/Endurance as an example of how this is supposed to work.

In the case of vehicle manufacturers, it is a guide to help them get the correct tire size and inflation pressure. They also need to gain experience. A good example is the Ford Explorer. At the time (1996 to 2000) it was common for SUV manufacturers to specify their tire pressures such that the GAWR's and the max load for the tire size/inflation were the same. They no longer to that. The tire size/inflation are now at least 115%.

Trailer manufacturers (including Airstream) are still on their learning curve. It wasn't but 3 years ago that ST tires were routinely failing and there was a lot of gnashing of teeth over this. Fingers were pointed every which way.

Many trailer manufacturers responded by specifying the max pressure, that way they could never be blamed if the tire failed. I think all the trailer manufacturers are still sorting this out.

So how do we apply this to the OP's situation? In a day or so, I will take the info in the OP and show why the 40 psi value is wrong.

Yeah, but the guy on the phone said....

[GCinSC2]

CapriRacer,

I’m reading and appreciating your .02$ worth.

Gary