Sjm9911 wrote:
I would say that the manufactures of the tires run there own tests and pass that info along with the results to get the ratings. Otherwise how would they come up with them? I don't think they guess. This is just the DOT testing and most likely does not represent the actual testing the tires go through by the manufacturers when they are conceived.
Allow me to confirm that tire manufacturers do their own testing, but they also do their own rating. DOT does only verification/ spot check testing. If they (DOT) find no issues, no one knows about the tests. If they (DOT) find an issue, they contact the tire manufacturer for clarification.
And just to be clear: Since we are talking about ST and LT tires, the load table is set by the tire standardizing organization - The Tire and Rim Association - and the tires are tested against that standard.
But for speed rating, there is an ATSM (SAE) test - again, conducted by the tire manufacturers for compliance to their published rating which DOT might test for compliance.
And just an FYI, for ST tires, the speed limitation for unrated tires is 65 mph, but there is no published speed limitation for unrated LT tires. Yes, this is a bit of a conundrum.
