My 2013 GMC 2500HD Duramax came with LT265/70R18 tires. I'm now on my second set of tires and looking for my third set. I've had good luck with the Michelin stock tires...no complaints. I stopped by to get a quote on new tires from my local tire shop. They told me the tires I want are on back order. They told me the LT275/65R18 were a more standard size and that I would like them better than the ones I was running. I understand the size difference...the tires they want to sell me are about 1/2 inch higher...1/4 inch on the diameter and about 1/2 inch wider. What I don't understand is...What are the real world changes I'll see on the highway running empty and pulling 12,000 lbs of 5th wheel? ... or are they close enough I won't notice any difference? Thanks in advance!