Many tires have a problem with "flatspotting" when allowed to sit for any amount of time, and BFG is one of the worst offenders. It has nothing to do with the compounding of the rubber, but rather with the construction of the carcass. The original belted T/A radial had absolutely HORRENDOUS flatspotting, due to the stiff construction of the belts. It would often take several miles for enough heat to build up in the tire to relieve the issue. Many performance tires (both radial and bias-ply) will do this, and it is less prominent in "regular" tires, due to their less-rigid construction. Even the tires on my Subaru will flatspot when I park it. Remember that, the more heat in the tire when it is parked, the more likely that the tire will flatspot. Long-term storage (more than a week) should still be done with the tires off the ground, because a flat spot can become a permanent annoyance. Plastics and synthetics seem to be the most prone to flatspotting, and steel belts appear to be the least prone to it. I hope this information is useful.
