When the tires touch on the sidewall the touching is not continuous but comes and goes as the tire rotates. There is a slight rubbing of the contacted tires as the tires flex slightly differently from a minutely different terrain under each tire. This generates the heat and friction on a part of the tire that was not designed to endure these forces.
I can understand that, but I don't know about rapid-overheating.... and it's not the same way as what 95 Stroker compairs. We have a 95 Dodge wrecker (I know, but it's a company truck
), that had a size too big of tire on it.... we could run it with a Geo on it and the tires would touch. We have pulled anything from 1/2 ton P/U's to UPS trucks up to 120 miles one way, and never had heating issues (MAYBE 10-20 degrees difference from rears to the fronts). Ran them enough miles the sidewalls were smooth.... but the newest set thet went on were the stock size called for (incase DOT ever stops us). Now, I'm not saying that I'm FOR running tires this way, just giving my .02 on them overheating. Thanks for the replies guys.