I have read may long threads here with people's opinions about various specific tires. I don't want to start another. But ...

My understanding of the TREADWEAR number printed on the sidewall of all non-snow tires is that it tells you how fast a tire wears down based on a Department of Transportation defined test. That would mean it can be used to objectively compare this specific aspect of tires across brands.

I have been shopping for tires and EVERY salesman tells me that the treadwear number can only be compared within a brand since each manufacturer tests to their own standards. I could believe that this is just a line inserted in all salesmen when they are spawned. I could also believe that the DOT number is a well intentioned government requirement that does absolutely no good. (Has that ever happened before?). But I would like to believe that I can ignore the hype and use these numbers (as well as the traction and temperature numbers) as a guide. Do any of you have solid information on this?
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Andy in St. Paul. '89 244 153K mi, '91 745 Regina 206K, '88 244 184K