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Old 09-26-2018, 06:22 PM   #21
Snoking
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Originally Posted by Tireman9 View Post
I am looking for the published Tire & Rim Yearbook that shows multiple load capacities (single application) for a single size tire and single Load Range for ST type tires. In my 40 years as a tire engineer I have never seen this so am looking to learn something new.
That is the standard for ST tires, that is nothing is standard. Inflated weight ratings were based on speed restrictions, then magically those speeds went up. As your fellow tire engineer Barry told me years ago, ST tires are not killing people when they fail, so the government has not stepped in.
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Old 09-27-2018, 08:32 AM   #22
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ST235/80R16 LR- has had a max load rating in US Tire & Rim Association standards book aka Yearbook of 3,420# since at least 2002.

While there have been "Technical Bulletins" issued in the past by Goodyear that allowed faster than 65 mph operation ( up to 70 and up to 75 mph) those deviations from the then current standard of 3,420# @ 80 were based on an increase in pressure with no increase in load capacity and also the increase in inflation and a 10% reduction in load capacity.


To my knowledge, the US TRA is the only tire industry standard organization that shows ST type tires. ST type tires are not found in Asian or European standards books.


I am still not able to find an industry standard that shows 3,500#



What GAWR is shown on the vehicle certification label? It is possible to have the axle have a higher rating but the RV company can de-rate various components to arrive at a GAWR such that the tire capacity equals or exceeds the GAWR. FMVSS does not require tire capacity to exceed axle capacity just as it does not require capacity be able to exceed the max load capacity of the springs or bolts or frame. If there was an exception letter issued on the tire capacity to NHTSA then clearly copies of that letter should have been given to the RV owner along with a warning that the only acceptable tire for the trailer would be of the identical size, load range, make and brand as the OE.
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Old 09-27-2018, 09:19 AM   #23
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Take a look at the Carlisle 235/80/R16E 3520 (124) @80 & 81mph
The same tire from Goodyear is 3420 (123) @80 & 85 mph or maybe 87mph
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Old 09-27-2018, 09:26 AM   #24
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Take a look at the Carlisle 235/80/R16E 3520 (124) @80 & 81mph
The same tire from Goodyear is 3420 (123) @80 & 85 mph or maybe 87mph



Yes Carslile ST235/80R16 LR-E does show 3,520 but with a 75 mph max


Interesting how ST tire mfg can magically all find both increased speed capability and load capacity for their ST line but can't make Passenger or LT tires better.
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Old 09-27-2018, 12:59 PM   #25
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If you step up to the 235/85x16 Endurance load rating is 3,640 at 80 psi
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Old 09-27-2018, 01:22 PM   #26
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If you step up to the 235/85x16 Endurance load rating is 3,640 at 80 psi



Yup but still 75 mph max operating speed.
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Old 09-27-2018, 03:03 PM   #27
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Yup but still 75 mph max operating speed.
Except the Endurance is rated N
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Old 09-27-2018, 11:13 PM   #28
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Tires with the DOT logo on their sidewalls must pass stringent physical and paperwork test/explanations. They are not known to all of us and some are very hard to find because of confidentiality, need to know or where to hunt for the answers.

The governing body requires all tire manufacturers to display all the major specifications about a tire right on its sidewall. They are not required to tell you why tire "A" is a little different than tire "B". All you really need to know is on each individual tire's sidewall. If you want to know more, you're going to have to search out the answers for your inquiry.

The following are excerpts rom FMVSS 571.109.

"Each tire shall conform to each of the following":

"Its load rating shall be that specified in a submission made by an individual manufacturer, for its size designation, type and each appropriate inflation pressure. If the maximum load rating for a particular tire size is shown in more than one of the publications, each tire of that size designation shall have a maximum load rating that is not less than the published maximum load rating, or if there are differing maximum load ratings for the same tire size designation, not less than the lowest published maximum load rating."


Note: Just in case you've never seen one, the Kenda Karrier ST235/80R16 LRE has a maximum load capacity of 3500#.
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Old 09-28-2018, 06:08 AM   #29
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I d9nt even know why the tire industry is speed rating any designated specific RV tire ... who in his right mind tows anything at 70 to 85 mph. It’s not smart and noth8ng will ever convince me it’s smart.. Tow at 65 max and give yourself and others time t9 react to unexpected road conditions..

Your tires will last longer .. for certa8n.
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Old 09-28-2018, 06:18 AM   #30
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I d9nt even know why the tire industry is speed rating any designated specific RV tire ... who in his right mind tows anything at 70 to 85 mph. It’s not smart and noth8ng will ever convince me it’s smart.. Tow at 65 max and give yourself and others time t9 react to unexpected road conditions..

Your tires will last longer .. for certa8n.
Yep, common sense you would think. Unfortunately, you know what "they" say about common sense...
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Old 09-29-2018, 01:47 PM   #31
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Tires with the DOT logo on their sidewalls must pass stringent physical and paperwork test/explanations. They are not known to all of us and some are very hard to find because of confidentiality, need to know or where to hunt for the answers.

The governing body requires all tire manufacturers to display all the major specifications about a tire right on its sidewall. They are not required to tell you why tire "A" is a little different than tire "B". All you really need to know is on each individual tire's sidewall. If you want to know more, you're going to have to search out the answers for your inquiry.

The following are excerpts rom FMVSS 571.109.

"Each tire shall conform to each of the following":

"Its load rating shall be that specified in a submission made by an individual manufacturer, for its size designation, type and each appropriate inflation pressure. If the maximum load rating for a particular tire size is shown in more than one of the publications, each tire of that size designation shall have a maximum load rating that is not less than the published maximum load rating, or if there are differing maximum load ratings for the same tire size designation, not less than the lowest published maximum load rating."


Note: Just in case you've never seen one, the Kenda Karrier ST235/80R16 LRE has a maximum load capacity of 3500#.

Sorry but ST type tires are not covered by 571.109 but are covered by 571.119




119 does have similar guideline of the tire capacity must equal or exceed 50% of the GAWR
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Old 09-29-2018, 01:58 PM   #32
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Sorry but ST type tires are not covered by 571.109 but are covered by 571.119




119 does have similar guideline of the tire capacity must equal or exceed 50% of the GAWR

What's your point? Mine is about designated sizes.
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Old 09-29-2018, 02:12 PM   #33
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I d9nt even know why the tire industry is speed rating any designated specific RV tire ... who in his right mind tows anything at 70 to 85 mph. It’s not smart and noth8ng will ever convince me it’s smart.. Tow at 65 max and give yourself and others time t9 react to unexpected road conditions..

Your tires will last longer .. for certa8n.

Speed ratings are directly related to how much a tire can safely carry at a designated speed. In theory, a tire rated at 65 MPH can carry it's maximum load capacity. When the speed increases beyond the 65 MPH, the tire is being fatigued and will degrade rapidly as the speeds increases.
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Old 09-29-2018, 03:01 PM   #34
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Speed ratings are directly related to how much a tire can safely carry at a designated speed. In theory, a tire rated at 65 MPH can carry it's maximum load capacity. When the speed increases beyond the 65 MPH, the tire is being fatigued and will degrade rapidly as the speeds increases.
Cal can you explain how the old 65MPH speed restriction is being push up without decreasing the load ratings of ST tires?
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Old 09-29-2018, 06:14 PM   #35
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Cal can you explain how the old 65MPH speed restriction is being push up without decreasing the load ratings of ST tires?

Only that the manufacturer's had to provide NHTSA with documentation to support the speed lettering they put on the tire's sidewalls.


I'll bet Tireman9 has an answer for this one....Wouldn't the damage done to a tire in a trailer position, operated beyond it's speed letter, be very similar to damage from under inflation?
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Old 09-29-2018, 06:44 PM   #36
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Only that the manufacturer's had to provide NHTSA with documentation to support the speed lettering they put on the tire's sidewalls.


I'll bet Tireman9 has an answer for this one....Wouldn't the damage done to a tire in a trailer position, operated beyond it's speed letter, be very similar to damage from under inflation?

That was not my question, it was how did they raise to speed rating and keep the same weight rating and in some cases even increase the weight ratng.
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Old 09-29-2018, 06:57 PM   #37
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Speed ratings are directly related to how much a tire can safely carry at a designated speed. In theory, a tire rated at 65 MPH can carry it's maximum load capacity. When the speed increases beyond the 65 MPH, the tire is being fatigued and will degrade rapidly as the speeds increases.
This is why I chose to run LT tire on my 5er. So many want more weight capacity in an ST, but run it at the max speed of 65 and wonder why the fail. Common sense tells me my tires rated for 3,042# at 106 mph (I believe testing standard is 85% of weight at full rated speed) then at 65 there is a bit of a weight capacity reserve. I am NOT saying that at 65 they can carry more than 3,042# just that it is well within the tires capacity. Common sense also says that load capacity, speed rating, and heat dissipation are all interrelated.
It is known also that LT tires are tested to stricter standards than ST tires.
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Old 09-30-2018, 09:03 AM   #38
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Cal can you explain how the old 65MPH speed restriction is being push up without decreasing the load ratings of ST tires?

IMO some tire companies think they use "Magic" tire construction that only works in tires with "ST" on the sidewall
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Old 09-30-2018, 09:14 AM   #39
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Only that the manufacturer's had to provide NHTSA with documentation to support the speed lettering they put on the tire's sidewalls.

I'll bet Tireman9 has an answer for this one....Wouldn't the damage done to a tire in a trailer position, operated beyond its speed letter, be very similar to damage from under inflation?



Speed symbol is NOT covered in FMVSS as far as I can tell. The DOT FMVSS test specified for ST type tires uses 88% of the tire max load (You never load your tires above that do you?) The test goes to 85 mph for 30 minutes then the tire is considered scrap. But if the tire hasn't "Blownout" at that point the company can claim it passed the High Speed test as far as DOT is concerned.





RE damage done
Underinflation can mean 20% low or 70% low. Different levels result in different failure modes and physical conditions. I have pictures of a "Blowout Real Life Experience" on my blog that I am not allowed to post here that shows the difference.
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Old 09-30-2018, 09:29 AM   #40
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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"....
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