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Old 01-28-2018, 09:59 AM   #61
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Why even have a tire inflation chart if the answer is to run at maximum tire pressure ? This is a bit confusing !
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Old 01-28-2018, 10:22 AM   #62
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Originally Posted by B Wilson View Post
Why even have a tire inflation chart if the answer is to run at maximum tire pressure ? This is a bit confusing !
I think I can answer that question.

Because some folks think they know better than the tire manufacturer and/or the vehicle manufacturer - and there are folks at the tire manufacturer who will do what the customer asks for without thinking about the implications.
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Old 01-28-2018, 10:26 AM   #63
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Sheer forces, spring rates, load limits.
I don't want a term paper, just tell me what tire pressure to run.
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Old 01-28-2018, 12:25 PM   #64
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http://www.tirefailures.com/cooperti...efailures.html
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Old 01-28-2018, 12:47 PM   #65
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Good Year Endurance = 75 PSI

Thank You, Mollysdad for asking the great question: Just tell me the pressure to run:

75 PSI
Lots of tolerance, up, down, high, low, hot, cold.

Will your pressure gauge measure accurately? I have tried multiple tire pressure gauges and they seem to vary.
What is measure cold: 20 F or 50 F, or 65F? Cold ambient could be all the above within the same day.
How much does the ambient air change in one day driving, so starting out in the 20's and hitting 65 in the afternoon, easy.
How precise 75? 74.5, 75.5, etc..... it reads 74.5 do you get out the air-compressor? Continue that thought, do you really get out the compressor for 74?
Weight per tire measure: front/ rear axle variances depending on the balance between front and rear
And everyone "says" they measure everyday. And many actually measure every few days when on a multi-day trip.
And for the most part we are talking dual axle Airstreams here.

So the short answer is:

75 PSI with GYE
Lots of tolerance.

& I expect lots of arguments.
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Old 01-28-2018, 03:23 PM   #66
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Originally Posted by CruizinDux View Post
Tireman9, If I understand your posts on various threads and here correctly, this is more of (if not entirely) an issue for dual axles as opposed to single axle bambi's? Maybe I misunderstood.

Thanks
Bob
Yes, the Interply Shear forces will be higher on multi-axle trailers than single axle trailers.
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Old 01-28-2018, 03:28 PM   #67
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To rephrase my question....
Is the shear going to be the same for a tire inflated to 55 lbs at maximum weight as a tire inflated to 80 lbs at maximum stated weight. Weight and inflation as stated in inflation chart.
The shape of the tire should be the same for both scenarios.

Sorry, it's not that simple. I can't make a knowledgeable statement on that scenario without re-running the computer algorithms.
My general statement is for reducing the shear in a given tire at a given load. I can't establish the shear force in pounds in one tire at one set of conditions to a different tire at different conditions based on the data currently available to me.
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Old 01-28-2018, 03:31 PM   #68
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Originally Posted by B Wilson View Post
Why even have a tire inflation chart if the answer is to run at maximum tire pressure ? This is a bit confusing !
What Capri said Plus
The charts help you to understand the capability for single axle use. Tables have been around for decades but the computer analysis is relatively new and is not well known in the tire industry and IMO probably completely unknown in the RV assembler companies.
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Old 01-28-2018, 03:34 PM   #69
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Quote:
Originally Posted by Mollysdad View Post
Sheer forces, spring rates, load limits.
I don't want a term paper, just tell me what tire pressure to run.
I and others have offered to answer that question to those that can provide
Complete tire size info and individual measured loads on each tire.

However, when we do that, there are many that want to argue and demand to know "WHY" we recommend the pressure we do and that leads to providing the background science.
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Old 01-28-2018, 03:40 PM   #70
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Originally Posted by GeeSag View Post
Thank You, Mollysdad for asking the great question: Just tell me the pressure to run:

75 PSI
Lots of tolerance, up, down, high, low, hot, cold.

Will your pressure gauge measure accurately? I have tried multiple tire pressure gauges and they seem to vary.
What is measure cold: 20 F or 50 F, or 65F? Cold ambient could be all the above within the same day.
How much does the ambient air change in one day driving, so starting out in the 20's and hitting 65 in the afternoon, easy.
How precise 75? 74.5, 75.5, etc..... it reads 74.5 do you get out the air-compressor? Continue that thought, do you really get out the compressor for 74?
Weight per tire measure: front/ rear axle variances depending on the balance between front and rear
And everyone "says" they measure everyday. And many actually measure every few days when on a multi-day trip.
And for the most part we are talking dual axle Airstreams here.

So the short answer is:

75 PSI with GYE
Lots of tolerance.

& I expect lots of arguments.

So if I were to measure 75.0 psi in a GRE in ST235/85R16 when the scale weight is 3,942# and tire is at Ambient temperature, you would declare all is good?
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Old 01-29-2018, 08:24 AM   #71
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For that question "So if I were to measure 75.0 psi in a GRE in ST235/85R16 when the scale weight is 3,942# and tire is at Ambient temperature, you would declare all is good?"

Who has 3,942 lbs on a tire in their Airstream? (Not per axle, Per tire)
They definitely need to follow the charts. Of course, they should not be running 75 psi on GYE-E-rated. But who has that kind of weight on their airstream? They are not the normal. For a dual axle, that would put them getting close to a 18,000 lb airstream trailer.
I doubt very many airstreams going down the road are in that kind of weight class.

Let’s go back to the question:
" Sheer forces, spring rates, load limits.
I don't want a term paper, just tell me what tire pressure to run."


To answer. Let’s narrow the focus:
Airstream only – this is an airstream forum. All those huge fifth wheels can go to some other forum.
This is Trailer only. GYE is a trailer tire, so we can filter out all the motor coaches.
Most Airstream trailers are dual axle. (yes, there quite a few Bambi’s and Base camps. But most are still dual axle)
Dual axle needs to be very much concerned about that sideways shear stress.
Popped Rivets are not good. So running Max may not be good if there is any truth to 80 psi has a higher incidence of popping rivets.
Belt separation at highway speed is Bad. Worse than popped rivets.
To minimize the chance of belt separation, it is probably better to run closer to the 80 psi, than not.
Is running 82 much worse than running 78 on those GYE’s rated for 80? Is being over inflated very bad? Is being over inflated worse than being slightly under inflated. If the tire was measured 80 cold at 20 degrees, is it over inflated at 65 degrees ambient? Is there any practical way to change once in route on a day when the temperature changes 20 to 60, or 60 to 95? It is hard to change once in route on a given day. So back to: Is it worse to be over inflated versus starting out slightly under when seeing large ambient temperature changes.


There have been many posts relative to these GYE anywhere from 65 PSI to Always run the Max (80).

There is no one simple answer.
Everyone must study the load rating charts and reach their own conclusion.

But with the large statistical sampling pool of Dual Axles airstreams in the 7600 GVWR range (and yes those much fewer Classic’s with 10,000 GVWR), there probably is a general averaging of what might be a good target pressure. I think there probably is a good rule of thumb for all those plus or minus 7600 GVWR airstreams out there.

The short answer is: Everyone MUST read the tire charts.
And we all still remain confused on how to balance all the Sheer forces, spring rates, load limits.

There is no one answer.

But there is statistical averaging based on the sheer number of dual axle late model Airstreams on the road.

The truth is out there!
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Old 01-29-2018, 09:10 AM   #72
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My trailer came from the factory with Load Range C tires inflated to 43 lbs (on the placard on the trailer, 1988 Excella 25').

Is it okay to run the Load Range E Goodyear Endurance at 45 psi?

Why do I really want a load range E tire?

What has changed to require 75 to 80 psi to hold up the same load that 45 psi used to do fine?

Goodyear lists a load range D Endurance. Is anybody running them or is the thought that the E has to be better?
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Old 01-29-2018, 09:27 AM   #73
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Quote:
Originally Posted by GeeSag View Post
Everyone MUST read the tire charts.
Yes, then throw them out and do what you think best.

Quote:
Originally Posted by Bill M. View Post
Goodyear lists a load range D Endurance. Is anybody running them or is the thought that the E has to be better?
Load rating D is not available in 15".
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Old 01-29-2018, 10:21 AM   #74
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Yes, then throw them out and do what you think best.

Load rating D is not available in 15".

It is for ST205/75R15.

There are only two Goodyear Endurance tires with a 15" rim
Endurance ST205/75R15 load range D
Endurance ST225/75R15 load range E

There are only two choices of Goodyear Endurance tires with a 14" rim
There are three choices for Goodyear Endurance tires with a 16" rim

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Old 01-29-2018, 10:26 AM   #75
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Quote:
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Load rating D is not available in 15".
I stand corrected. GYE are not available in 15" in the size that fits my Airstream.
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Old 01-29-2018, 06:17 PM   #76
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Does anybody have a New Airstream that shipped from Airstream with GYE?

What is the recommended PSI, tire size, and GVWR?

If so, let's see what Airstream recommends?

I thought I had seen a blog post somewhere that the new Airstreams are shipping with GYE.
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Old 01-29-2018, 06:48 PM   #77
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Quote:
Originally Posted by GeeSag View Post
Does anybody have a New Airstream that shipped from Airstream with GYE?

What is the recommended PSI, tire size, and GVWR?

If so, let's see what Airstream recommends?

I thought I had seen a blog post somewhere that the new Airstreams are shipping with GYE.
There's a Tire Placard on the side of your trailer with that info.
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Old 01-29-2018, 09:57 PM   #78
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Quote:
Originally Posted by GeeSag View Post
Does anybody have a New Airstream that shipped from Airstream with GYE?

What is the recommended PSI, tire size, and GVWR?

If so, let's see what Airstream recommends?

I thought I had seen a blog post somewhere that the new Airstreams are shipping with GYE.
Here’s a data point (or two) for you.

Our 2017 23D FC came with GYM’s with 65psi on the tire sidewall. The sticker on the trailer says to inflate the tires to 65psi.

We saw a 2018 23CB FC (new name for the 23D) at an rv show last weekend. It’s has GYE tires (80 psi on the sidewall). The sticker on that trailer said “80psi”. Keep in mind that this trailer is identical to our 2017 23D.

My conclusion: Airstream just copied the sidewall pressure from the tires they supplied and put it on the placard. The psi listed on the trailer placard didn’t come from some analysis that Airstream engineers performed. There’s nothing magic about it.

If I were to put GYE’S on my trailer I’d probably inflate to 75 or 80 psi. Although this question is moot since I’m going to the 15” Michelin’s. I’ll inflate those to the sidewall pressure, which I’m sure won’t match the 65psi on the placard.
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Old 01-29-2018, 10:09 PM   #79
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Quote:
Originally Posted by GeeSag View Post
Does anybody have a New Airstream that shipped from Airstream with GYE?

What is the recommended PSI, tire size, and GVWR?

If so, let's see what Airstream recommends?

.
Airstreams come in lots of different lengths. So it would be difficult to answer the question on PSI and tire size. That is different for different trailers. I would doubt the tire size has changed much from GYM to GYE on Airstream trailers as long as the GVWR of the trailer has not changed.

Since GYE tires were introduced about a year ago, I am pretty sure GYMs are no longer available to anyone since that point. Except in dealer store inventories where turn over is not frequent for trailer tires. Airstream likely has a contract with Goodyear in the Airstream models that they install a ST tires. Heck both companies are in Ohio.

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Old 01-30-2018, 06:49 AM   #80
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I'm not sure the factory has this tire thing figured out any better than any of us. They used to ship 23FBs with 14" D rated tires. (GYMs) When they switched to GYEs they went with 15" tires on the same trailer (good move on their part) but went to E rated tires. The weight of the 23FB didn't change, the D Endurance tires are available, but they went to E anyway. It's about a 700 lb higher rating. I'm going to go with the E tires, but inflate them at the D rated 65# instead of E rated 80#. There is about $11 difference per tire. I wonder how much difference is in the actual construction of the tire. The outside diameter it 1.2" larger on the Es.. Is that just from the additional air pressure? Ha! I think it's possible to overthink this a little.
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