Last week I addressed the topic of tire age. Some are still asking why there isn't a better and clearer age limit on tires in RV use. It may help if there is a better understanding of the complexities of what is involved in making the prediction.
I think that most can understand
that the numerous variables involved such as ambient temperature,
operating temperature, load, and operating speed all can affect the
"life" of a tire. Also there is the obvious variation in the numerous
components and assembly practice of each tire itself. All of this adds up to an impossibly complex equation if trying to predict the life of a tire.
many may understand that if a tire spends its life in Arizona, Texas,
Alabama, Louisiana or Florida, it will have a definitely different
life span than one that spends its life in New England, even if the
load, inflation and speed were magically identical. I do wonder how many
have even a passing understanding of the complex nature of
manufacturing a tire as seen in THIS animated video. Actual shots of the process are here. Here is an alternate view of the truck tire process, which would be essentially identical to what is seen in both LT and 22.5" size tires. If you watch only one video, IMO this 3rd one is the best and most informative.
materials like steel or aluminum, rubber is not a homogeneous material
so even minor variations in the raw materials can affect raw material properties and ultimately tire life.
Here is a video
showing the basic process of preparing rubber before it is applied to
steel or polyester cords. Note these are videos of very low tech
methods. Modern equipment is much larger and the process is harder to
see as there is much more automation behind closed chamber shields.
estimates of maximum tire life are based on assumptions of the
variability of the tire and the variability of the use of the tire. The
estimate must also consider the probability of the variables stacking up
and the potential for the severity of the tire failure.
Some companies may feel that no greater than 0.5% probability of failure at 7 years is acceptable IF
the tire is always operated in North America, never exceeds its max
speed rating or is overloaded for the inflation in the tire. Another
company may feel that less than 5% at 12 years is the goal.
also important to remember that only after thousands of tires have
completed years of service can a company know if it made the correct
calculations. I do not know of any company that is not constantly
working to lower the failure rate or extend the usage time while
at the same time trying to meet customer demands for better wear, fuel
economy, traction, ride and lower cost, and the order of priority for these and other variables the customer wants in their tires.
While compromising safety is never a consideration, the rank order of the dozens of performance characteristics can have an effect on tire life.
Here is a challenge with hypothetical information. Would all RV owners be happier if they were told that the maximum age of tires was 8 years BUT it would be illegal to operate on a tire older than 8 years or operate without a load, temperature and pressure monitor and recording system "black box" system and tire warranty would only be good 4 of the 8 year life? Oh ya, the "black box" monitor system would add $500 to the initial cost of the RV and there would be a required annual fee of $75?
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