Is the Goodyear Endurance ST type tire "Better Quality" than a Goodyear LT tire?

Had a couple of comments on my post on LT vs ST type tires for RV trailers

Alan said

"Now, I am VERY confused. For years, everyone in the RV business, its commentators, its experts and other blogger forums so-called experts “having used this or that for soooo many years without any problems”, etc, had me convinced in believing all the hullabaloo about the ST tire’s sidewalls being much better, much stiffer and much more resistant to the particular type of flexing that occurs when driving, turning and parking travel trailers or fifth wheels than LTs. After the appearance of the “china-bombs syndrome” a few years ago, people started to realize that practically all ST tires were manufactured in China anyway, whatever the
“US brand name” stamped on them, leaving the consumer with very few, if any, alternatives.
Now, coïncidentelly, we hear that LT tires are “just the thing” for trailering.
It also appears that a handful of RV manufacturers, like Jayco, have seemingly struck a deal with Goodyear, who now has resumed manufacturing ST tires in North America, to equip their new trailers with “US-made ST tires”. I guess their ST tire prices have dropped again enough to catch the big manufacturer’s attention and make it worth their while.
So I guess the real question should now be, are US-made Goodyear ST tires better, worst or equal quality than their US-made Goodyear LT tires, or why even bother to engineer ST tires at all? We shall see, in time, who wins between; Beta or Vhs, Plasma or Lcd, Android or Apple, etc, etc, etc."


Alain, The biggest issue is, I know of no way to do a direct comparison of ST vs LT tires other than an expensive tire test. We can't depend on the DOT test results. In all probability the tires all pass, simply because the RV industry and ST tire mfg companies were successful in getting ST tires excluded from the significant improvement in testing with updated standards in 2002. There is no question, in my mind, that the tests (FMVSS 571.119) for ST type tires are easier to pass than the tests (FMVSS 571.139) for new Passenger and LT type tires.
I have looked at the construction of a GY Endurance and it certainly looks better than the older Marathon design. Now remember I do not have access to the actual specification or material properties used by GY but in the Endurance tire line, they appear to have added a Nylon cap over the steel belts. You can confirm this by reading the material list molded on a tire sidewall.

"Quality" is a tough call when you have two different specifications to start with. Isn't Quality just a measure of a tire's ability to meet the specification for that product?

You can think of it this way.  If I had two pieces of chain. One rated at 500# and another rated at 550#. They both meet a strength test of supporting the rated load and if you tested 100 pieces of each and found that all 100 passes the rates strength test how would you rate the 'Quality"? You can't say the 550# chain is better quality than the 500# chain as they have two different goals, just as you can't say a 1-ton truck is better quality than a 1/2 ton truck because the 1-ton can handle more load.

Your example of Beta vs VHS is a good example of the confusion possible. Beta was judged technically superior to VHS but Sony made a marketing decision to prevent other companies from using the Beta specification in their video players. The result was that VHS units were less expensive so many people bought on price. Eventually, Sony lost out. Not because the "Quality" of that video format wasn't as good as VHS but because the market was "price-sensitive" and too many people selected lower cost over better quality product.


Gene offered
"OK, color me confused! I have always gotten the impression that ST tires and not LT tires are what I should be running on my RV. After reading this article now I’m not sure. Are you suggesting that all things being equal, LT tires of the same size, load rating, etc are better to run on my RV? I don’t mind the cost, just want to put best possible tire on my RV. Thanks for keeping us informed."

to which I replied

Gene, The problem is that "all things are not equal" as there are no LT tires of the same size, load range, and load rating, etc as an ST tire. There is always something that is different.
Sometimes the only option would be to go with larger size LT tires but in some cases, there is no physical room to run the available larger size tires.

IMO, what you "should" be running are tires built to the latest industry test standards (LT) that can offer at least 15 to 25% "Reserve Load " capacity

When you "upgrade" the Load Range, what inflation to run on trailer?

Another question from RV trailer owner "I am replacing the tires on my small (12-14 ft, depending on how you measure) travel trailer. I plan to buy Good Year Endurance ST205/75R14, load range D to replace the brand X Chinese ST205/75R14, load range C.

Vehicle manufacturer says to inflate to 50 psi. Sidewall on existing tires have 50 psi listed as max.

The replacement Good Year tires have max of 65 psi on the sidewall.

I see that the opening post on this thread says to use the sidewall pressure. But I have always gone with the vehicle maker's suggestions which are often lower than the max tire rating. For example, my F-250 wants 65 psi in front and 80 in the rear.

Do I use the 65 max on the tire or with the vehicle manufacturer's 50 psi?"

So I said:   Simple question but I can make the answer complex.

The MINIMUM inflation you need to run is what the Load Inflation tables show for the actual measured load on your tires.

Lacking the actual scale reading, we need to look at your RV certification label that identifies the MINIMUM inflation your trailer mfg recommends. This is based on the DOT requirement that the tires be capable of supporting the GAWR load as shown on the label.

RVIA (Recriational Vehicle Industry Association) in 2017 started to require a 10% Reserve Load (Load capability more than the GAWR minimum).

As a tire engineer, I come at the topic of trying to provide the best conditions to allow the tires to run the longest. As I cover in my this blog post, trailers place extreme shear forces that are 24% greater than similar forces experienced on motorhomes. This, IMO is the primary reason for tire life in trailer application being less than on motorhomes.

Also, you need to remember and understand that it is the air pressure, not the tire sidewall that supports the load. If you run the inflation used in LR-C tire in a LR-D tire, you will have no increase in load capacity so will gain nothing.

Having said all this I would suggest you run at least the certification label +10%.  If you can run label +20% that should result in better durability.

See that wasn't too painful.

##RVT912

New GY Endurance only available in higher Load rating. What to do?

Hello Roger,
At the end of next season I plan to replace our GY Marathon tires after 5 seasons and about 20K miles and have been thinking of the new Endurance tire. However, the specs. are somewhat different between them and am not sure what to do.

Our Marathons are LR-D ST225/75R15.  I always run them at sidewall max. pressure 65 psi. The max. load rating is 2540 lbs and gives us about 30% reserve load capacity. The required rim width is 6-7”. The standard tires for our make and model of travel trailer are an unknown brand LR-C and the Marathons were an available option so we upgraded to them. No issues whatsoever with them. I do not know what the max. psi rating for our rims is without taking one off. They are 6-lug.

I like the idea of having a 225 wide tire vs 205 because I *think* it may provide better handling from lateral forces in curves. I have our TV & TT set up for better handling including shocks on the TT. It performs very well in twisty mountain roads at speeds up to 65 mph.

If we were to get the new Endurance tires in an ST225/75R15 width, it means going to LR-E tire which have a max. 80 psi rating. The load rating increases to 2830 lbs. Required rim width is still 6-7”. The increased reserve load capacity would be fine. I have no idea if our rims are rated for 80 psi and would have to remove a wheel. I believe in the practice of running the ST tires at the sidewall max. pressure to get max. reserve load capacity.

If we were to go with an Endurance tire in a 65 max. rating, it would mean going to a LR-D 205 wide tire and the max. load rating drops to 2150 lbs. I do not want to reduce the reserve load capacity that much and would rather not have to go to a skinnier tire.

What to do if going to Endurance tires? If our rims are only rated to 65 psi, could I simply reduce the LR-E pressure to 65 psi? Have not looked at load tables to see what this does. Or stay with LR-D and have skinnier tires and substantially less reserve load capacity? Are tires rated for and inflated to 80 psi going to result in better handling or perhaps an undesirable harsher ride for the trailer? Not sure why GY did not make the Endurance a direct one-to-one swap for Marathons. It looks like GY no longer offers the Marathon?

Comments would be greatly appreciated.

+++++++++

My reply:

Your 30% reserve load capacity is good. I wish other trailer owners had as much. You may not see any benefit in increasing the reserve load above the 30%. The reserve is based on actual scale readings, yes?

I would not go down to the ST205 @ 65 psi.

I see no problem with running the Endurance ST225 LR-E @ 65 until or unless you confirm higher rim psi rating. It may not be marked on the wheel and I doubt the wheels are "brand name". When you change tires you can look for anything that might ID the wheel such as part number. If the wheels are only 65, then 65 is OK.

Yes, in my posts on Interply Shear I have suggested increasing inflation, but your CIP should not exceed the rim rating (all ratings are for cold inflation pressure).

LR-E ST225's have same load capacity when inflated to 65 psi as do ST225 LR-D at 65 psi.

Hope this info helps. 

New Goodyear Endurance pressure & temperature question

Saw this question on temperature and pressure increase on a new set of Goodyear Endurance tires.

"Took our first trip with the new Goodyear Endurance tires.
Trailer rode great, better than the old tires.
So, on this first outing I closely monitored the TPMS to see if there were any differences in the readings I had with the old tires.
Obviously, the first difference was the starting "cold" tire pressure. (65 psi vs the old 50 psi)
The first thing I noticed was how quickly the tire pressure increased once we got on the road.
87 degree day, 60-63 mph, tire pressure on sun load side got to 75psi (73 - 74 psi on shaded side). Tire temp got to 96 - 97 degrees (99 degrees on one tire briefly).
This compares to the average 5 - 8 psi increase I experienced on a typical trip with the old tires.
This brings me to my question.
Is a 10 - 12 psi increase in pressure considered acceptable? If so, what should I set the high pressure alert at on my TPMS?"

My reply:
The temperature and pressure changes are reasonable for most 14" - 16" RV tires, especially trailer  applications, but I will focus on your question.

Not sure if your "test" is "scientifically" sound -- You were comparing two different tires (LR-C vs. LR-D) and a new tire vs. old used tire.

New tires will always run hotter than old tires.

With nominally dry air the pressure will increase by about 2% for each +10F. One other related item is that aftermarket external TPMS are not reporting the temperature of the hottest areas of the tire which is internal to the structure. Also while it may not seem reasonable, it has been demonstrated that the temperature of the air inside a tire is not uniform. It is also known that the metal body of valve stems and the metal body of the sensor will be cooled as it whips around in outside ambient air which will result in a lower reading.

In all probability your tire is actually 20 F to 30 F hotter than the TPMS is reporting, but this is within the expected design limits considered by tire engineers.

New tires do run hotter than old for a couple reasons. Extra stress as initial cross-link chemical bonds are broken as tire is "broken in." This takes about 100 miles. New tires have deeper tread depth, which will also make a tire run hotter, which means more pressure growth.  Your GYE have extra components (mass) in the tread. Read the sidewall and I believe you will see Nylon cap plies in the tread which were not in the old GYM tires. This is another contributor to more heat.

To your question on pressure increase setting for TPMS. As I covered in my blog post on TPMS settings I figure that +25% from baseline is a reasonable number, but obviously the pressure you select for your baseline may affect the top number.

Bottom line. Your numbers look normal and acceptable.

##RVT806

Goodyear Endurance ST tire info

I have been in touch with Goodyear and while there are still some technical details that need to be clarified, I have permission from GY to post the info sheet and the Load & inflation chart. (Click on each image for a much larger view.)