Goodyear Endurance tires

[Tireman9]

Originally Posted by JRTJH

Here's a hypothesis, not a process:

The tire rating states: "Meets or exceeds ..." So, is it possible (or probable) that the manufacturer initially tested the tire line at X weight/Y speed/Z pressure which was 15% over the stated rating. They then tested the tire line at X weight/Y+10 speed/Z pressure and it didn't fail, but it was only tested at 5% over the stated rating. In this situation, the tire meets the increased speed rating, but not by the "exceeds" amount that the same tire line "exceeded the rating" at the lower speed ???

I'm guessing, can't provide any facts and don't really care, just watching the "can you prove it?" challenges that the three of you "tire experts" are tossing around. My hypothesis is that the tires were initially tested at 65MPH and exceeded the weight rating by 15-20% before failure. Then, with all the competition, they tested the same tires at 75MPH and they exceeded the weight rating by 3% (my guess) before failure, so they changed the speed rating. Same tire, greater speed rating, no changes made, but still "meets or exceeds" the minimum rating, so "good to go"....

Sorry but FMVSS 119 has not changed. Still only requires 85 mph for 30 min at 88% of sidewall max load. Just as it did 10 years ago. The "Endurance test spec hasn't changed either.

[JRTJH]

Originally Posted by Tireman9

Sorry but FMVSS 119 has not changed. Still only requires 85 mph for 30 min at 88% of sidewall max load. Just as it did 10 years ago. The "Endurance test spec hasn't changed either.

I'm not suggesting that any of the testing procedure has changed... Reread what I did suggest: The advertising statement has always been: "This tire meets or exceeds the standard"....

What I suggested is that the tires met the test standard and had a 15% additional margin. So, the manufacturers increased the speed rating and the tires still meet the standard, but now only with a 3% additional margin.

We do that ALL the time in medicine. When we were kids, people got a tetanus vaccine every 3 years. Now, we get one every 10 years. The way we "reached the new standard" is by increasing incrementally, nobody dies for a tested period of time, so we increase another increment, nobody dies, increase again. So far, we've eliminated smallpox vaccinations, increased tetanus vaccination and changed childhood vaccinations.

I wonder not if the standards for testing have changed, but if the tires are the same and with the increased speed rating, the tires still "meet or exceed" but not by the previous margin but by a lesser margin?????

[Tireman9]

Originally Posted by JRTJH

I'm not suggesting that any of the testing procedure has changed... Reread what I did suggest: The advertising statement has always been: "This tire meets or exceeds the standard"....

What I suggested is that the tires met the test standard and had a 15% additional margin. So, the manufacturers increased the speed rating and the tires still meet the standard, but now only with a 3% additional margin.

We do that ALL the time in medicine. When we were kids, people got a tetanus vaccine every 3 years. Now, we get one every 10 years. The way we "reached the new standard" is by increasing incrementally, nobody dies for a tested period of time, so we increase another increment, nobody dies, increase again. So far, we've eliminated smallpox vaccinations, increased tetanus vaccination and changed childhood vaccinations.

I wonder not if the standards for testing have changed, but if the tires are the same and with the increased speed rating, the tires still "meet or exceed" but not by the previous margin but by a lesser margin?????

OK, I understand your concept. The problem is I don't know how to "exceed a "Step Speed" test and translate a non-specified step into a speed capability that is not part of the test.


FMVSS 119 High-Speed test says

"S7.4 High speed performance. (a) Perform steps (a) through (c) of S7.2.
(b) Apply a force of 88 percent of the maximum load rating marked on the tire (use single maximum load value when the tire is marked with both single and dual maximum loads), and rotate the test wheel at 250 rpm for 2 hours.
(c) Remove the load, allow the tire to cool to 35 °C (95 °F), and then adjust the pressure to that marked on the tire for single tire use.
(d) Reapply the same load, and without interruption or readjustment of inflation pressure, rotate the test wheel at 375 rpm for 30 minutes, then at 400 rpm for 30 minutes, and then at 425 rpm for 30 minutes.
(e) Immediately after running the tire the required time, measure the tire inflation pressure. Remove the tire from the model rim assembly, and inspect the tire."


The RPM converts to 50mph, 75 mph, 80 mph & 85 mph so the steps are not linear. What would you consider exceeding the specified test by 15% look like? run 34.5 minutes at 85 or run another 30-minute step at 97.75 mph?


The Speed test above is required for a variety of tires with ST being one type. LT and Pass tires have different standards and different test requirements.


None of the DOT tests support any "Speed Symbol" claim as DOT doesn't recognise the speed symbol.
SAE high-speed test is not a regulatory test.

J1561_200102
"This SAE Recommended Practice provides a method for testing the speed performance of passenger car tires under controlled conditions in the laboratory on a test wheel. This procedure applies to “standard load,” “extra load,” and “T-type high-pressure temporary-use spare” passenger tires."


Maybe you can explain how

a P235/75R15 would be rated for 1,874# @ 32 psi and can carry an "S" speed symbol (112) but in trailer or pick-up service is only rated to carry 1,703#
An LT225/75R15 is rated for 1,445# @ 35 psi and can carry an "S" speed symbol
Then we see an ST225/75R15 is rated for 1,760# at 35 psi with a Speed Symbol of "N" (87)


If you only want to look at dimensions, load & inflation I don't know why all three wouldn't be rated for 1,703 to 1,760# load capacity.
Why haven't the tire companies put the same better construction features they apparently are putting in the ST tires in the LT tires? where load capacity is an important factor in selecting the vehicle?


The high load capacity in ST tires was developed based on a stated 65 mph Max speed. The addition of higher speed ratings was not accomplished with improved engineering but because of Import Tarrifs being imposed on non-speed rated tires by US Dept of Commerce in 2017 and as if by magic each and every tire company making ST type tires almost overlight added high speed capability to the tires. There were no years of incrimental improvements in speed capability. If that were the case we should have seen so 70 mph tires then 75 etc but we didn't.

[JRTJH]

I can't explain it, maybe if I could, I'd claim to be a "retired tire engineer" and write confusing posts about tires on trailer forums. That's not said to 'slight you" but to say that in two posts, you've not yet even addressed my comment. Maybe I'm being "elementary" in my thinking, maybe I'm understanding my theory and you simply don't understand it.

What I'm saying is that X tire company makes a ST tire rated at 65MPH to carry 2380 pounds at 80 PSI. Their competition changes the speed rating to 75 MPH at the same weight/pressure. They look at the failure rates (percentage of tires that failed and at what part of the test process) and make the determination that their tires will meet that same speed rating based on their test results. They realize that speed=heat=wear=failure and they determine that based on the standardized testing that they can increase the speed and still meet the heat=wear=failure and maintain the failure rate below the acceptable standard. Doing so, they increase the speed rating, knowing that the failure rate will likely increase, but that increase will remain below the acceptable rate......

Seems simple to me, as long as they don't reach the NHTSA imposed threshold that requires a recall, they're "golden" (or at least silver or maybe bronze) at any rate, they're selling tires and not facing government imposed recall action. That seems to be the goal. It's never been about "zero defects" but "acceptable losses while maintaining profit margins".....

[Tireman9]

Originally Posted by JRTJH

I can't explain it, maybe if I could, I'd claim to be a "retired tire engineer" and write confusing posts about tires on trailer forums. That's not said to 'slight you" but to say that in two posts, you've not yet even addressed my comment. Maybe I'm being "elementary" in my thinking, maybe I'm understanding my theory and you simply don't understand it.

What I'm saying is that X tire company makes a ST tire rated at 65MPH to carry 2380 pounds at 80 PSI. Their competition changes the speed rating to 75 MPH at the same weight/pressure. They look at the failure rates (percentage of tires that failed and at what part of the test process) and make the determination that their tires will meet that same speed rating based on their test results. They realize that speed=heat=wear=failure and they determine that based on the standardized testing that they can increase the speed and still meet the heat=wear=failure and maintain the failure rate below the acceptable standard. Doing so, they increase the speed rating, knowing that the failure rate will likely increase, but that increase will remain below the acceptable rate......

Seems simple to me, as long as they don't reach the NHTSA imposed threshold that requires a recall, they're "golden" (or at least silver or maybe bronze) at any rate, they're selling tires and not facing government imposed recall action. That seems to be the goal. It's never been about "zero defects" but "acceptable losses while maintaining profit margins".....

Yup except there is no NHTSA "Threshold" other than all (100%) of tires sold must be capable of passing the NHTSA specified tests. Zero margin on that.


In the real world what we find is that people do not maintain the inflation, or run heavy or hit pot holes or run fast etc etc.
People will almost never admit to not checking the air with an accurate gauge every stop. They "know" they have never overloaded their tires.
Then there is a failure and people complain. Some may even file complaints with NHTSA. I know of no "red line" of number of complaints forNHTSA. IMO sometimes it may be workload or a TV report or similar and someone starts to look and find complaints. Lawyers get hungry and before you know it you have a law suit. I have never heard of a defence of " We only have x% failures so you can't sue us" working in court.


If I remember correctly the Ford Explorer investigation started after a TX TV news item. BUT I bet if that TV item had happened on 9/10/2001 the news the next day might have meant the Explorer activity might never had surfaced.
Is it possible that some ST tires can run faster than 65 at the stated load? probably but for how long? At how much under inflated?


What hasn't been addressed is why tires in trailer application do not have the same life as tires on Motorhomes or cars? ( 5 to 7 or 10 years seems to be the norm in those RVs and while there are occasionally trailers running ST tires that get long life, I would bet significant money that you would find most replace tires at 3 to 5 years to avoid the higher failure rate that occurs at 4 to 6 years rather than ar 8 to 12 years.


But anyway. There is nothing stopping folks from running whatever speed/load/inflation they want. All I would ask is that when you choose to follow your own hypothysis of why tires fail you don't ask me or the other tire engineer on-line to explain why.


Happy RVing.

[Javi]

Just for grins... the RPM conversion to MPH is entirely dependent on tire diameter... bigger more MPH... smaller less MPH for the given RPM … but okay..

[JRTJH]

Originally Posted by Tireman9

Yup except there is no NHTSA "Threshold" other than all (100%) of tires sold must be capable of passing the NHTSA specified tests. Zero margin on that... All I would ask is that when you choose to follow your own hypothysis of why tires fail you don't ask me or the other tire engineer on-line to explain why.Happy RVing.

Really???? "don't ask me or the other tire engineer on-line to explain why".

I sense your frustration with this thread. Just as a reminder, there has never been a "Dear Tireman9" on any of my posts, I simply stated my "hypothesis" in an open forum, postulating, much the same as you and other posters in this thread. Suggesting, "don't ask me or the other tire engineer on-line"... ???? Who the heck are the other "tire engineers on-line" and why would you think I asked you anything until you responded to my hypothesis? If you can refute it with facts, please do, I'll listen, if you're going to quote government regulations that mandate a process but don't address how or why businesses circumvent those regulations by building loopholes that allow them to function in the gray areas and then ask me to not ask you why??? Well, that boat won't float or to keep it "RV related" That trailer won't drag.....

It almost sounds like you're approaching the issues/questions/comments from a narrow black and white "engineering perspective" without opening your field of vision/field of thought to include the "gray areas" in which every business makes decisions behind public scrutiny. Companies don't (even though in an ideal world they should) bring products to market to be the best or the most reliable, they bring products to market to make more money for the stockholders than their competition. If, along the way, they just happen to become the best or the biggest or the most popular, that improves their profit beyond the "least investment for the greatest return" philosophy that drives every "profit oriented business".

Not that this example relates to tires, but just compare Harbor Freight to Snap-On and you'll see that there are two entirely different product quality philosophies. Two entirely different "product quality profiles" both of which sell to their customers and make a profit. It's the same with tire companies. Not all make management decisions based on "quality and reliability". Some make decisions to bring products to market that are "not the best, but good enough" and sell at a lower price than "the best".... There's a niche for cheap ST tires with a 65MPH speed rating and if the company can market them at 81MPH without changing their product cost or their reputation and without facing a recall action, they'll increase profits and maintain their market share.

Do you really believe that TowMax sells tires with their reputation on this forum as a concern? As long as they're selling tires, they couldn't care less what any of us think. After all, "we" don't buy the tires, Keystone does and sells them to us without our permission.... Sort of a "perfect relationship" for TowMax, eh? As long as NHSTA doesn't recall TowMax tires with the 81MPH speed rating, they compete with Carlisle and Goodyear and sell cheaper while making a profit. How they do it may be magic, lies, computed risks or outright deceit, whatever, it's a risk the company is willing to take to maintain their market share.

[Snoking]

A look at ST tire history of failures will clear the fog. Just ask Cal about his failure record if you want a clearer picture of the past history of ST tires.

[Tireman9]

Originally Posted by Javi

Just for grins... the RPM conversion to MPH is entirely dependent on tire diameter... bigger more MPH... smaller less MPH for the given RPM … but okay..

Nope, it the RPM of the 67.23" dia test wheel

[ctbruce]

Hmmmmmmmmmmm......

[Javi]

Originally Posted by Tireman9

Nope, it the RPM of the 67.23" dia test wheel

So where would the MPH be measured, I guess irrelevant to the actual tire. If that's the case it would not be relevant to the speed of the given tire. And giving a MPH equivalent is worthless to the discussion.

Because a larger diameter tire would have less revolutions per mile and thus be running a a much higher mph.

[sourdough]

Originally Posted by JRTJH

I can't explain it, maybe if I could, I'd claim to be a "retired tire engineer" and write confusing posts about tires on trailer forums. That's not said to 'slight you" but to say that in two posts, you've not yet even addressed my comment. Maybe I'm being "elementary" in my thinking, maybe I'm understanding my theory and you simply don't understand it.

What I'm saying is that X tire company makes a ST tire rated at 65MPH to carry 2380 pounds at 80 PSI. Their competition changes the speed rating to 75 MPH at the same weight/pressure. They look at the failure rates (percentage of tires that failed and at what part of the test process) and make the determination that their tires will meet that same speed rating based on their test results. They realize that speed=heat=wear=failure and they determine that based on the standardized testing that they can increase the speed and still meet the heat=wear=failure and maintain the failure rate below the acceptable standard. Doing so, they increase the speed rating, knowing that the failure rate will likely increase, but that increase will remain below the acceptable rate......

Seems simple to me, as long as they don't reach the NHTSA imposed threshold that requires a recall, they're "golden" (or at least silver or maybe bronze) at any rate, they're selling tires and not facing government imposed recall action. That seems to be the goal. It's never been about "zero defects" but "acceptable losses while maintaining profit margins".....

Well, anyone that knows me and my posts know that I try to speak straight. The dialogue between Tireman9 and most everyone else seems to be mostly vague, but, more in the vein that if you run ST tires they are failures and can't measure up. I'm just paraphrasing because I've read so many of the convoluted posts that I'm not really sure what is being said or what I've read. In short order we had Snoking and Tireman9 show up and start ripping ST tires and anyone that might condone them.....so they come in doubles? Are we shooting clays?

[rhagfo]

I only wish that tire makers like Michelin, Bridgestone,Hankook, and Yokohama would make LTs in F & G capacity’s would solve a lot of tire issues.

[JRTJH]

Originally Posted by rhagfo

I only wish that tire makers like Michelin, Bridgestone,Hankook, and Yokohama would make LTs in F & G capacity’s would solve a lot of tire issues.

I wonder if the reason they don't build them is because the tires that thick in smaller sizes would create problems with heat dissipation? Sort of like having a "double fat kid" that's 3' tall. He'd have to sweat twice as much as the same weight kid that's 6' tall. Since tires can't sweat, they'd have to be able to shed the heat some other way. If they couldn't cool themselves, they'd overheat and degrade faster than thinner tires that can rid the heat more efficiently.

Often it seems we tend to take one technology and apply the rules that come with it to a different technology and expect the rules to apply even though the product is different, built with different components and characteristics.

I'm sure skid steer tires would hold up well to carry the weight of a travel trailer, but could they hold together at 75MPH? They are 16, 18 and 20 ply tires. They work great at 5 or 6 MPH, not so much at 75MPH. With their limited sidewall flex, most travel trailers would shake apart in the first 100 miles of towing. Without the flexing in the tires, the trailer suffers, add the flexing, the tire can't dissipate heat as well and self destructs. Maybe the balancing act of managing both sidewall flexing and heat dissipation is the reason you don't see a 14 ply LT tire as OEM on private vehicles. Maybe someday the technology will evolve. I don't think it's there yet.

[Tireman9]

Originally Posted by Javi

So where would the MPH be measured, I guess irrelevant to the actual tire. If that's the case it would not be relevant to the speed of the given tire. And giving a MPH equivalent is worthless to the discussion.

Because a larger diameter tire would have less revolutions per mile and thus be running a a much higher mph.

Was gonna let this slide but just could not resist.


The surface speed of the test drum running at 250 RPM can be measured in mph even with no tire on it.


We are not talking about rpm of the tire. The drum dia is constant.


Maybe someone else can explain the relationship of surface speed of a test drum to drum RPM better.

[Javi]

Originally Posted by Tireman9

Was gonna let this slide but just could not resist.


The surface speed of the test drum running at 250 RPM can be measured in mph even with no tire on it.


We are not talking about rpm of the tire. The drum dia is constant.


Maybe someone else can explain the relationship of surface speed of a test drum to drum RPM better.

I understand that Dilbert... But that has no relationship to actual tire speed as far as I can tell... Can you develop the relationship to the individual tire speed... I am an actual mechanical engineer... not a tire engineer

[flybouy]

For the ease of math, let's say the drum has a circumference of 3' or 1 yard. There are 1760 yards to 1 mile. So in order to have the surface of the drum moving at 60 m.p.h. (1 mile/minute) the drum would have to rotate at 1760 r.p.m. The actual r.p.m. of the tire would be dependent on the circumference of the tire. No matter what size the tire is, it would be spinning at the m.p.h. of the drum. m.p.h. is a measure of time over distance and not r.p.m. if the circumference is variable. Hope that convoluted explanation helps.

[rhagfo]

Originally Posted by flybouy

For the ease of math, let's say the drum has a circumference of 3' or 1 yard. There are 1760 yards to 1 mile. So in order to have the surface of the drum moving at 60 m.p.h. (1 mile/minute) the drum would have to rotate at 1760 r.p.m. The actual r.p.m. of the tire would be dependent on the circumference of the tire. No matter what size the tire is, it would be spinning at the m.p.h. of the drum. m.p.h. is a measure of time over distance and not r.p.m. if the circumference is variable. Hope that convoluted explanation helps.

Excellent explanation of a simple concept, some people way over think stuff.

[Javi]

Originally Posted by flybouy

For the ease of math, let's say the drum has a circumference of 3' or 1 yard. There are 1760 yards to 1 mile. So in order to have the surface of the drum moving at 60 m.p.h. (1 mile/minute) the drum would have to rotate at 1760 r.p.m. The actual r.p.m. of the tire would be dependent on the circumference of the tire. No matter what size the tire is, it would be spinning at the m.p.h. of the drum. m.p.h. is a measure of time over distance and not r.p.m. if the circumference is variable. Hope that convoluted explanation helps.

I understand the relationship of MPH to Circumference of the test drum... But that still doesn't explain HOW that references the TIRE... If you put a 31" tire in the test drum the diameter of the tire will dictate the distance relationship to the tire itself.. The rotational speed of the drum is only part of that equation..


Actually...


31” diameter tire will have to turn 650 RPM to do 60 mile per hour


31 x 3.1416 = 97.3896


63360 / 97.3896 = 650.583 revolutions per mile




Multiply the diameter of the tire by Pi to get the circumference of the tire and then divide the inches in a mile (63,360) by the circumference of the tire.. that gives you the revolutions per mile... after that it's easy..

I think I studied this in 5th or 6th grade, but that was a long time ago...

BTY the test drum is turning 299.987 revolutions per mile..

[flybouy]

I think your mixing the 2 measurements, m.p.h. vs r.p.m. Placing a tire on the surface of the drum is no different than placing it on the road. Think of the drum as the road wrapped around a shaft. If you think about your truck pulling a small utility trailer or boat trailer. Your truck can have 33" tires andthe trailer 8" tires, going down the road the r.p.m. of the tires will be vastly different but both vehicles, and their tires are going the same m.p.h. The smaller tire will be spinning at a faster r.p.m. in order to to travel the same distance as the large tire.

Edit ... The tire test is rating the tire in relation to speed in m.p.h., not the r.p.m of the tire, under a load that is dictated by the letter classification as a minimum. At least that's my understanding.