2009 Chevy Silverado 2500HD, gas, 17" on Z71 package. Sticker on door jamb is missing, don't see a chart in owners manual specifying for the 17". New Michelin Defenders but same size as the 17" OEM...also same 'E' load rating. Never paid much attention to the old tires, but tire shop (per TPM) set these at high 40's front and mid 60's rear. Where is the best place to get a definitive answer? Dealership?