Per Lindgren <lindgre@ONLINE.NO> wrote:

"I have a small opinion about the need for HD LT 8-ply C-rating tires, instead
of passenger car tires. The real trick is to find tires with the right load
index. Those big luxury cars don't drive on truck tires, and they weigh more
than a Vanagon. The BMW 750 uses 235/60 WR 16, the weight is 2070 kg. The MB S
600 runs on 235/60 ZR 16, weight: 2190 kg. The Rolls-Royces wear 235/65 VR 16 on
the rims, they weigh from 2400 up to 2800 kg. The Chrysler T&C minis use 215/65
SR 15, they weigh around 1700 kg, and I'll bet that NONE of this cars use truck
tires, go with passenger tires, as long as you get the right load index, which
by the way is 97 for Vanagons."

So an empty Westy Vanagon weights 4900 pounds, or about 2225 kg.  Then families
pack it with gear, lash the boat on the roof, and all get in.  The center of
gravity is higher than those autos you cited, and the stress on the sidewalls
when turning close to the limit of what the vehicle will go is not equivalent to
those cars either.  Were you only running them empty and straight, I'd find your
argument much more compelling.
John