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Old 06-11-2019, 07:39 PM   #37
CWtheMan
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Join Date: Feb 2010
Location: Taylors, SC
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Quote:
Originally Posted by Tireman9 View Post
OK Here is kind of my overview of tires.
1. The basic format for load capacity is Size (air volume) x PSI x K
2. The "K" is supposed to be a factor that relates to the tire service. If a tire is normally run with a 25% Reserve Load (to account for occasional low inflation or high load) on the improved highway for 3 to 5 years, you might have a high K factor like 1.1. On the other hand, if a significant portion of the population of tires will be operated under-inflated or overloaded and you want 10 years life then the k should be a lower value like maybe .80. But what happens when the vehicle design imparts excess belt stress sometimes 24% higher than seen on normal motor vehicles? The K factor should be reduced significantly. Maybe even 24% to 0.65

2. The RV industry lobbied long and hard to not upgrade the durability improvements that were placed on P and LT tires in 2002. Why? They didn't want to spend more on tires. DO they care more about their bottom line than you having no tire problems? What do you think? They didn't have a tire problem. They followed the standards instructions. The tire industry had the problem by allowing tires without any load capacity reserves to be used as OEM on RV trailers.

3. The ST load formula was based on a MAX speed of 65 with normal highway speed of 55. (IMO the tire manufacturer's are using a different formula. What else would explain the ST tire industry wide speed ratings going to as high as 87 MPH? Is NHTSA looking the other way?
4. Given that the RV trailer travels at the same speed as the tow vehicle, why would you expect people to slow down when the strong engine can easily pull at 80 mph?
5. What is the difference between an LT tire and an ST tire today? They both travel at the same speed on the same roads. The LT only needs to last 4 to 5 years but the RV tire does not wear out till 10 years + in many cases.
6. Under what logic would you expect a tire with the letters "ST" on the sidewall to be able to carry 20% more load than a tire with the letters LT on the sidewall. The physics of Size x PSI still holds but now the operational speed of the LT and ST are the same. (Carlisle CEO told Modern Tire in an interview that ST tires use larger & stronger cording. Do you have information that makes that untrue?)
7 If there were some magic rubber that allowed a company to make tires that can carry 20% more load (the difference between LT and ST) Why wouldn't the company put that "Super" compound in their premium LT tire line? (Just maybe the different stresses in the LT design wont permit it...The load capacity of the GY G614 RST LT235/85R16 LRG comes to mind.

8 Only a few tire companies make ST tires. Ever wonder why? (Labor Costs.)Do you think it's possible that they do not want to make tires that they can be fairly confident will not live long enough to wear out before they fatigue? Why would you make a product where a majority of the users abuse your product? Even if you do not warranty the product for more than a year it certainly doesn't make people feel confident in your brand, does it? Read the new Triangle USA ST tire warranty.)
If I were King I would do away with ST type tires and require a 20% load margin on LT type tires in RV trailer application and require TPMS on all RVs.


But I'm not King so all I can do is offer suggestions to help people get better tire life.
Most of the ST tire manufacturers are right up front with providing ST tire life expectancy.

There are numerous posts where the writer makes comments about ST tire mileage. They are not mileage tires. I've never seen ST tire warranty for mileage.

I've always said a tire's warranty is a good indicator of its manufacturers confidence in the tire's durability. Many of todays tire warranty packages - all designs - are very comprehensive and worth reading.
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