A question came up about the Max speed recommendation as published by Goodyear, Michelin, and Bridgestone for tires in RV use.
To help clarify:
Many times the "application" or use of an item results in it additional or different limitations or ratings.
If I have a tire that is a 225/75R15 and inflate it to 35 psi, How much load can it carry?
If the intended use is on a passenger car 1,874#
If as a single on an LT it is rated for 1,445#
If as a dual on a LT 1,315#
If a Single on a trailer where having passengers in the trailer is actually prohibited 1,760#
and if in a dual application on a trailer 1,570#
Part of the decision process for a tire's capacity in each of these different applications includes such things as:
Will the vehicle carry passengers? Is the "Reserve Load" of the tire in the application normally close to zero or maybe 10% or normally closer to 25%
An obvious example where the application affects the load capacity is well established in the use of "P" type tires on a truck, trailer or multi-use vehicle such as an SUV. In these applications the load capacity is reduced by Industry standards by dividing by 1.10 so the 1,874# capacity becomes 1,703#
For heavy truck there are published guidelines that allow an increase in load capacity if the max speed is significantly reduced. As the speed is lowered the load capacity can be increased up to 16% with no increase in inflation.
Similar to above if the tire is made for a specific market a tire company my have more demanding requirements on the tire during the development process. An example might be it the tire was being made for a market where the speeds and Ambient temperature was both very high the tire might require a more robust construction. Another example might be providing a special tread rubber if the tire was to be used at extremely low temperatures where the tread rubber might even crack if a "High Speed" rated tire tread were used.
Tires are much more complex than many people suspect. Ideally, an owner would be more informed and knowledgeable about tires and their limits and capabilities when making a purchase. They are much more than just "Round Black" things that almost no one "wants" to buy.