I am not so sure about that. According to “Tirerack”..
“….it is important to realize that the Department of Transportation does not conduct the tests. The grades are assigned by the tire manufacturers based on their test results or those conducted by an independent testing company they have hired. The NHTSA has the right to inspect the tire manufacturer's data….”
“..Typically, comparing the Treadwear Grades of tire lines within a single brand is somewhat helpful, while attempting to compare the grades between different brands is not as helpful.’’
http://www.tirerack.com/tires/tirete...currentpage=35