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Old 03-27-2019, 12:06 PM   #113
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Barry and I are the only two actual tire engineers on this forum as far as I know.

Neither of us work for GY but we both worked for many years at two other major tire companies. We both understand the physics of tire performance.
The load tables are published every year.



I do not recall ever seeing any change in load capacity for a given size once it is in the published book. So tha answer is... No, tire load capacities are basically fixed based on physical size ( air volume) and service type ( P or LT or ST) and do not change over the years.



If you think GY has some "magic" tire construction that suddenly allows both an inflation reduction and a load capacity increase don't you wonder why they don't use that "magic" in their first line P and LT type tire?
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Old 03-27-2019, 09:14 PM   #114
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Just When i thought i understood this stuff i think i read the link in my earlier post (#33) at least 5 times before it clicked...apparently i'm not hearing well.

Never understood why the chart indicated 87 on a 65 rated ST ( GYE 225/75/15e)

First off, to be clear i have no plans or desire to tow at 87mph...breaking the 65 threshold only in brief spurts when passing. The exception and not the rule. My sweet spot is about 62-63.

My scale weight per tire, using the higher ds/cs value x2 and then adding the required 15% margin puts me at about 70-72psi. I run at 75. They retain pressure incredibly well and very. few rivets popped.

Just so i understand this, if i wanted to tow at 87, i don't need to add additional pressure to get me from 65 to 87.....because the N rating on the gye E tire already gets me there. Is that correct? I was thinking my math above got me to 65.

Thanks

Bob

[Sort of.

Ya see, LT tire load charts are also predicated on a 65 mph speed restriction - HOWEVER - if an LT tire has a speed rating that speed rating becomes the speed limitation - AND - since pretty much all LT tires have them, the 65 mph speed restriction doesn't apply.

The same is true of ST tires. If an ST tire has a speed rating, the 65 mph speed restriction is replaced by the speed rating - and as gypsydad pointed out above, he is using Goodyear Endurance ST tires which have an N speed rating (87 mph).[/QUOTE]]
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Old 03-28-2019, 06:24 AM   #115
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Originally Posted by CruizinDux View Post
...… Just so i understand this, if i wanted to tow at 87, i don't need to add additional pressure to get me from 65 to 87.....because the N rating on the gye E tire already gets me there. Is that correct? I was thinking my math above got me to 65. ….
Yes, that is right.

But I think the best way to look at this is that while 87 mph is the upper limit for an N speed rated tire, doing so eats up all the reserve - making it more likely that a failure will occur.

Ya' see, this is all about REDUCING the risk of failure. There isn't a clear, bright line between failure and non-failure. The line is very fuzzy and anything there are many things that can be done to improve the odds
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Old 03-28-2019, 09:21 AM   #116
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Perfect, thanks CR. Yours and TM9's feedback is very much appreciated.

I have no interest in pushing the limits but prefer to minimize all rizk.

Bkb

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Originally Posted by CapriRacer View Post
Yes, that is right.

But I think the best way to look at this is that while 87 mph is the upper limit for an N speed rated tire, doing so eats up all the reserve - making it more likely that a failure will occur.

Ya' see, this is all about REDUCING the risk of failure. There isn't a clear, bright line between failure and non-failure. The line is very fuzzy and anything there are many things that can be done to improve the odds
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Old 03-28-2019, 10:31 AM   #117
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The comfortable reserve the ST tires even , make me wonder if on airstream tires last as long as LT tires , so 6 years or more.
And not the sometimes 3 to 4 years ,as they five for ST.
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Old 03-28-2019, 10:40 AM   #118
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Point of clarification.

The Tire & Rim Association Load formula used by the industry for ST type tires is based on a 65 mph max operating speed. Neither P or LT tires have stated max speed as part of the formula section of the TRA "Engineer Design Information" aka EDI book.
P-type have the stated 1.10 "De-Rating" of load capacity when used on a trailer or P/U.
LT tires have no de-rating when placed on trailer nor do they get an "up-rating if placed on passenger car so we could consider LT kind of the standard for load capacity.


If you look at similar physical sized tires and include the P Derating you will see the de-rated P and LT tires give similar results for load capacity.

BUT the load capacity of the ST type is significantly higher. Why would that be if there were not some other controlling factor i.e. the 65 mph speed limit? Some people would have us believe that ST tires all had some magic rubber added to them in 2017 when speed ratings higher than 65 were added. The reality is that the speed rating was added to avoid import tariffs.

Maybe you think that all the different tire companies used this "magic" rubber to give them an overnight increase in speed capability.
Why isn't there a single tire company anywhere in the world using this "pixie-dust" in their LT or heavy truck tires to give them an extra 10% to 25% more load capacity?


I have examined a section of a GY Endurance and it clearly has "better" construction than some non-speed rated tires. Only time will tell if this new construction results in a better life and if so how much better.



What I have not seen is anyone changing their advice on tire life in RV usage. What trailer company now says up to 10 years life or even claims over 5-year life?
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Old 03-28-2019, 02:28 PM   #119
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Tireman9 wrote
I have examined a section of a GY Endurance and it clearly has "better" construction than some non-speed rated tires. Only time will tell if this new construction results in a better life and if so how much better.
-load

Have you compared the sectrion of Endurance E-load with ST D-load, then the better construction is yust to hold more pressure in.
Have you compared them with same sise E-load LT tire, then probably pretty similar construction and the higher maxload then that LT E-load can only be because of the still 65mph for wich the Endurance is calculated , in compare the LT for 99mph mostly.


the aditional service descriptions that are given in Europa on most Trucktires, ( fi 156K and additional 154L) is also only because of the speed its calculated for and not the "magical dust" that only works up to 110kmph belonging to K speedrating.
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Old 03-28-2019, 03:36 PM   #120
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R we confusing each other yet?? (or just having fun!) Knowing the limits by the Mfg. is one thing; I certainly would not be pushing the limits at 87mph! But, as I mentioned about materials used, sidewall and tread construction, and Mfg. load/pressure limits, is good to know and understand. We all know that an ST tire has stiffer sidewalls then an LT tire, and clearly more than a P rated tire, right? Stands to reason the lateral load is much greater on a TT (thus the stiffer sidewall construction), then on a pickup or passenger vehicle. It's great to get the experts agreeing on following the Mfg. chart on the Endurance...thanks for sharing your experience!
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Old 03-29-2019, 09:59 AM   #121
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R we confusing each other yet?? (or just having fun!) Knowing the limits by the Mfg. is one thing; I certainly would not be pushing the limits at 87mph! But, as I mentioned about materials used, sidewall and tread construction, and Mfg. load/pressure limits, is good to know and understand. We all know that an ST tire has stiffer sidewalls then an LT tire, and clearly more than a P rated tire, right? Stands to reason the lateral load is much greater on a TT (thus the stiffer sidewall construction), then on a pickup or passenger vehicle. It's great to get the experts agreeing on following the Mfg. chart on the Endurance...thanks for sharing your experience!

Many talk about sidewall stiffness in ST tires as the side load flexing is visually obvious. But as I cover in detail on my Interply posts all these forces have to go through the belt package and the structural failure due to these side loads manifests with belt separations, not sidewall failures.



RE Speed. Few realize the Speed symbol is based on an SAE Passenger tire test which in a 30-minute step speed test. If you feel passing a 30 min test at 87 is an indication of cumulative minutes at such speeds then go ahead. I just don't want to be anywhere nearby. Speed generates heat. Heat damages the rubber strength and such damage is cumulative and never repairs itself but only gets worse.
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Old 03-29-2019, 10:09 AM   #122
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Endurance Tire pressure on 27FB Int'l

Yup. The speed rating should be thought of as absolute maximum on a brand new tire for short periods of time.

Why push your luck with sustained speeds close to that limit which is checked one time on a prototype tire. Besides, the speed limit for towing a trailer is not that high.

In California, vehicles towing are supposed to be going 55 mph, not the full speed limit. Of course, it’s “more in the breach that the observance” out there.

It’s disconcerting to see an obviously overloaded monster toy hauler on the ball of a piddling small pickup truck go past at over 70, on a windy day, heading downhill. Even in my car I avoid those fools like the plague they are...
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Old 03-29-2019, 11:16 AM   #123
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The reality is that the speed rating was added to avoid import tariffs.

I'm not following this thought. What do speed ratings have to do with avoiding tariffs?
I thought the speed rating was upped due to the redesigned ST tire? Carlisle redesigned their ST tire which now (2017) has a higher speed rating but it is still made of "Chinesium".
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Old 03-30-2019, 05:13 AM   #124
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The comfortable reserve the ST tires even , make me wonder if on airstream tires last as long as LT tires , so 6 years or more.
And not the sometimes 3 to 4 years ,as they five for ST.
This post was written a bit to quick on mobile.
I expect manny Airstream users to make 6 years or more with the ST tires, because of the comfortable reserves, even if maxload calculated back to 99mph.

So question here is for those who use adviced / prescribed pressure of mostly 65 psi, what livetime without tire-troubles they make??
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Old 03-30-2019, 03:35 PM   #125
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I'm not following this thought. What do speed ratings have to do with avoiding tariffs?
I thought the speed rating was upped due to the redesigned ST tire? Carlisle redesigned their ST tire which now (2017) has a higher speed rating but it is still made of "Chinesium".

A few years ago (2015) Import tariffs were imposed by the Dept of Commerce on some tires. Some tires were excluded. Tires with speed ratings were excluded. At the time ST tires had no speed rating. By adding a speed rating to ST tires they could avoid the tariff.
Speed ratings were not imposed by DOT as a safety issue. The speed ratings and possible re-design of some tires (GY Endurance is different than the GY Marathon based on the section of tires I have seen) came about AFTER the final rule for the duty (tariff).
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Old 04-01-2019, 12:28 AM   #126
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Originally Posted by jadatis View Post
This post was written a bit to quick on mobile.
I expect manny Airstream users to make 6 years or more with the ST tires, because of the comfortable reserves, even if maxload calculated back to 99mph.

So question here is for those who use adviced / prescribed pressure of mostly 65 psi, what livetime without tire-troubles they make??
Topicstarter is already one who did 6 years with his , I supose ST tires, without any problem.
So who follows.
Also those who made that with lower pressure, fi 55 psi, please answer.
Give also maximum speed used, wich you did not go over for even a minute.
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