The Towmax STR Powerking 235/75r16E's that came on my fiver made it about 3 years and 4k miles before two of them failed. Luckily, between traffic lights, a guy got my attention to let me know that I had a huge bubble on the side of one of them. He certainly saved me from a blowout. So now I'm researching replacement tires and the general consensus seems to be that ST tires are crap and the thing to do is go to an LT. I'm looking for some good advice in this area. What have you tried? What should I stay away from?
2012 F250 SD CC SB Fx4 Lariat 6.7 PSD
1995 F150 XL 4wd 5.0
Depends on the weight of your 5ver. If it has 6k axles, then the Michelin XPS Rib is the number one choice followed by Bridgestone Duravis. If you have 7k axles, the Goodyear G614's are the best but expensive at around 325 per. The second choice in this class is the Sailun S637 which is about half the price. Both the Goodyear and Sailun are G rated tires and require rims that are rated to 110 lbs PSI. Rims are generally stamped on the back side with their max pressure. I personally run he Goodyear's and now only think about tire failures when reading about them on the forums... Hope this helps....
PS If your rims are only rated to 80 psi and you are on 7k axles, then your best bet is to pass on the G tires and go straight to a 17.5 tire and wheel package. Good package deals can be found at trailertiresandwheels.com.
I went straight to G614's.. (had the dealer install them before pickup) Goodyear has a very good reputation for paying for repair of rv damage cause by tire failure (keep the carcass until they tell you that you don't need it). Sailun does not have that kind of coverage.
I also just added a TST TPMS system to my truck and trailer.
and my enclosed car hauler too. (E tires on twin 3500 lb axles).
I went from 235/80-16 ST tires to 235/85-16 E rated Cooper tires. If you do a study on how tires are rated, under what conditions and what the difference in the testing standards are between LT and ST tires you will understand why many RV'ers do the same.
I chose Cooper because they are produced in the USA where you will not find an ST tire that is not an import in a 16" tire size.
Do the research for yourself, be comfortable with your decision and go LT.
FWIW, our 5th wheel with Power King or whatever the China brand was had two blow outs in less than 1K miles and they were new.
A Great wealth of information here from a gentleman from when I post this same question on an RV site.
This debate will be entertained until there are no more RV's, so with that, for inquiring minds with an afternoon of spare time to read and research the references, here is one of the best informative writings on the ST vs LT that I have read. I copied it from a post on the Montana owners site where a very lively discussion ensued for days.
Here is the info a guy compiled from the government site on tire testing....
SUMMARY OF FINDINGS & CONCLUSIONS
I found the testing requirements for both the ST and LT tires at the Federal Motor Carrier Safety Administration (FMCSA) webpage.
The testing for each tire is comprised of (1) bead unseating resistance, (2) strength, (3) endurance, and (4) high speed performance.
The testing for (1) bead unseating resistance and (2) strength were identical for tires representative of moderate to heavy 5th wheels and thus no advantage is given to either tire type.
The testing for (3) endurance was found to be significantly different between the ST and LT tires.
Both the ST and LT are put through the same initial pressure, time and load profile. The total profile lasts 34 hours of continuous run time starting at 85% of rated load and ending at 100% of rated load. To further stress the tires, a load range E tire (nominal 80 psi rating) is tested at a reduced pressure of 60 psi to induce additional load on the tire during testing. (This is reasonable that testing should be conservative.)
But now the endurance testing diverges significantly.
The ST tire is tested at this pressure, time and load profile at 50 mph. After that, the ST test is over.
The LT tire is tested at this pressure, time and load profile at 75 mph. This is a 50% increase over the ST and will induce significant additional load and heating on the tire during testing. After that, the LT test is not complete. Next a Low Inflation Pressure Performance test is performed for the LT tire only. The tire pressure is decreased to 46 psi and the tire is immediately run for an additional 2 hours at 75 mph and 100% of rated load.
Thus, the LT tire endurance test is drastically more intense than the ST endurance test.
The testing for (4) high speed performance.
The difference in high speed performance testing between a ST and LT tire is significant. Both tires are tested through a 90 minute speed/time profile.
The ST tire is tested 88% of rated load while the LT tire is tested at 85% of rated load. Thus, the loading is 3% higher based on rated load and this slight advantage goes to the ST tire.
However, the LT tire is tested at significantly higher velocities when compared to a ST tire (99 vs. 85 mph maximum speed). This is a 16% advantage to the LT tire.
Thus, again the overall test for the LT is more rigorous than the ST test.
It is reasonable to conclude that these test requirements force the tire manufacturer to construct an LT tire more substantially than an ST tire. This is also a reasonable explanation for the same size LT tire is rated at a slightly lower maximum load than a ST tire.
And now, for those of you who need to know all the details, read on!
Each standard for the ST and LT tires has definitions, significant constraints on labeling, etc. that I will not address. There are also tire conditioning (temperature), tire break in, etc. that are the same or similar for ST and LT that I will not address. The details are in the references.
The (3) endurance, and (4) high speed performance tests must not result in tire failure. Tire failure includes visual evidence of tread, sidewall, ply, cord, inner liner, or bead separation, chunking, broken cords, cracking, or open splices, not just a blowout.
TESTING - BEAD UNSEATING RESISTANCE
ST Tire: (reference paragraph S5.2.2)
The tire is mounted horizontally and a vertical load is applied to the tires outer sidewall at a rate of 50 mm (2 inches) per minute.
Increase the load until the bead unseats or a specified value is reached.
Repeat the test at least four places equally spaced around the tire circumference.
Paragraph S6.6 Tubeless tire bead unseating resistance references the ST tire procedure noted above.
The testing for bead unseating resistance is identical for a ST and LT tire.
TESTING - STRENGTH
ST Tire: (reference paragraph S126.96.36.199)
Force a 19 mm (3?4 inch) diameter cylindrical steel plunger with a hemispherical end perpendicularly into the tread rib as near to the centerline as possible, avoiding penetration into the tread groove, at the rate of 50 mm (2 inches) per minute.
Compute the breaking energy for each test point by means of a provided formula.
LT Tire: (reference paragraph S6.5.2)
Each tire shall comply with the requirements of S7.3 of 571.119, which is tires for vehicles weighing 10,000 lb or more. Per S7.3 of 571.119 for our example tire, the testing is the same as the ST tire procedure noted above.
The testing for strength is identical for a ST and LT tire.
TESTING - ENDURANCE
The following is for a ST or LT tire of less than nominal cross section less than or equal to 295 mm (11.5 inches) which is typical of a 5th wheel application.
ST tire: (reference paragraph S5.4.2)
There are specifications for the contact of the tire mounted on a test axle and steel test wheel after the test that I will not address because they are similar for the ST and LT.
Inflate a load range E to 60 psi. (410 kPa)
Conduct the test at 80 kilometers per hour (km/h)(50 miles per hour) in accordance with the following schedule without pressure adjustment or other interruptions:
The loads for the following periods are the specified percentage of the maximum load rating marked on the tire sidewall:
Time and Percent of rated load
4 hours, 85%
6 hours, 90%
24 hours, 100%
LT Tire: (reference paragraph S188.8.131.52)
Conduct the test, without interruptions, at the test speed of not less than 120 km/h (75 mph)
Inflate a load range E to 60 psi. (410 kPa)
This test uses the same profile as the ST tire.
Immediately following the above sequence perform a Low Inflation Pressure Performance test (reference paragraph S6.4):
This test uses the same tire/wheel as the previous sequence at a reduced pressure.
For a load range E tire the pressure is reduced to 46 psi. (320 kPa)
The same tire/wheel is run an additional 2 hours at the reduced pressure at a speed of 75 mph and 100% of rated load.
The difference in endurance testing between a ST and LT tire is significant. Both tires are tested through a equivalent loading/time profile. However, the LT tire is tested at this profile at a higher speed (75 vs. 50 mph) and must still endure an additional 2 hour low pressure test without failure. Thus the overall test for the LT is far more rigorous than the ST test.
TESTING - HIGH SPEED PERFORMANCE
ST tire: (reference paragraph S5.5.4)
Load the tire to 88 percent of the tires maximum load rating as marked on the tire sidewall. Inflate to 72 psi (500 kPa). Run the test sequentially without interruption at:
75 mph (121 km/h) for 30 minutes
80 mph (129 km/h) for 30 minutes
85 mph (137 km/h) for 30 minutes
LT Tire: (reference paragraph S184.108.40.206.7)
Load the tire to 85 percent of the tires maximum load rating as marked on the tire sidewall. Inflate to 72 psi (500 kPa). Run the test sequentially without interruption at:
87 mph (140 km/h) for 30 minutes
93 mph (150 km/h) for 30 minutes
99 mph (160 km/h) for 30 minutes
The difference in high speed performance testing between a ST and LT tire is significant. Both tires are tested through a speed/time profile. The ST tire is tested 88% of rated load while the LT tire is tested at 85% of rated load. Thus, the loading is 3% higher based on rated load and this slight advantage goes to the ST tire. However, the LT tire is tested at significantly higher velocities (nearly 100 mph!) when compared to a ST tire. This is a 16% advantage to the LT tire. Thus, again the overall test for the LT is more rigorous than the ST test.
Actually, that's a common misconception. RST is just the name and in no way is referring to an ST tire. G614's are LT tires as stated on their website. Goodyear even put out a bulletin explaining this but I'll be damned if I can remember where I saw it... They were originally designed for HD trucks like tow trucks and also approved for trailer use. Since these type trucks no longer run 16" rims Goodyear officially changed their "position" usage to trailer but their history is still hinted at with their LT designation.
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