Tires on ??
Frankly, perhaps because I parked a variety of vehicles - RV, ATV, trucks, etc., for extended periods of time in Alaska, prefer gravel. In cold weather, tires tend to flatten on the bottoms creating a flat area that takes, sometimes quite a few miles (depending on how long they'd been sitting and outside temp) to "round out". Additionally, I've had, because of rain, snow, then low temps, the flatter surfaces freeze to the tire causing chunks of rubber to stick to those flat surfaces, separate from the tire and eventually "chunk off" the tire, obviously reducing tire integrity. Reasonably course gravel precludes that because the tire isn't freezing to an even flat surface; the gravel's uneven surface allows water to drain and reduce freezing surface. Mechanicsburg's winter temps may ameliorate that condition, but I see no reason I can think of (other than a storage facility's requirement) to store your RV on a completely flat surface.
