Tireman9 wrote:
OK If you insist. {Getting on my soap box}
I get a bit miffed to see the misguided efforts of those who have neither the training or experience of being responsible to design a tire that meets both DOT requirements, their own company requirements and the customer requirements which conflict with easily meeting the previous two requirements and do it for $25 material cost while also being constrained my manufacturing limitations.
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K is NOT a Safety Factor. It is more like a service factor based on historical expected service that type and size tire will experience.
The statistics of a "margine of safety" needed to ensure all tires will pass the specific DOT test is based on historical variability of the test results for the specific tire in question and not on how many miles a tire is expected to run in service.
The biggest problem tire manufacturers have is the users that refuse to check the inflation and ensure the tire is loaded properly and that the vehicle is in alignment. Out of alignment can cause not just irregular wear but can cause premature tire failure.
Now before I provide the correct formula to those who want to be tire engineers,I would ask that those who are trying to reverse engineer the tire load capacity let the rest of us know:
1. The size tire they are running
2. The inflation they set the tires to before each trip
3. The actual load for each tire
4. DOT serial of their tires
5. When they had their pressure ga calibrated and it's accuracy.
When I see at least four posters provide the above minimum
info I will give the correct formulas from Tire & Rim Association.
I will leave it up to FE to provide the details of the different government test requirements for ST vs LT type tires. We don't need to go into P type ot TBR type at this time.
Bottom line. If you can't be bothered to confirm you are not overloading or out of alignment or that or have an accurate pressure ga and can't be bothered to inflate your tires before each trip I'm really not interested in spending a lot of time trying to convince you that you can solve many of your problems by simply following the owners manual.
If you got stuck with tires that only meet the bare minimum of the requirements you need to face up to the fact that you are going to have to pay the consiquences for your purchase decision. You will need to change your tires and may have to change wheels also.
If you are running the inflation associated with the max load as molded on your tire but need more load or speed capacity then you probably need to change from ST type to LT type but when you do so you MUST confirm that the increased inflation you will probably need to run with the LTR will require a wheel capable of handling that load and inflation. Stop worrying about K factors or hoping someone will decide to ignore decades of history using certain tables and formulas. Just not gonna happen.
Ok I feel better. Hope I didn't offend anyone as that was not my intent. I just believe that we can be more productive if we try and address specific issues and problems rather than try to re-invnet the wheel, and tire.
All very well and succinctly said, Tireman!
May I suggest one addition to your (above highlighted) list?
Seems like the speed at which folks habitually tow is important, especially as regards heat buildup.
Might that info be important to include in your assessment?
