Over the last 23 years I've gone through lots of tires on lots of vans. The 
only ones I will use now MUST have an LT or C6 rating, and take a maximum 
pressure of 50psi. ANYTHING else is too squirrelly (ie all over the road, 
dead/alive) on corners. The tapioca effect was a good description. BUT you 
don't need to follow the VW specs and run at rated (by VW) pressures. I 
adjust the pressures for load and /or speed. Normal, daily, unladen driving 
I run 36psi all around. This is good for brief highway excursions. The C6/LT 
tires don't 'slap' so hard on the pavement cracks, and it doesn't feel like 
I need new shocks from ride harshness. Long distance highspeed, add 2psi, 
fully loaded, goto VW specs. You can also drop your tire pressures in winter 
if you need some added traction, makes a bigger footprint, but put it back 
up once conditions change.
         A nasty little note for Vanagon owners.... check the MAX psi rating 
ON YOUR SPARE before you pump it up to door label specs. My spare 
(Continental) was identical to the mounted tires but was rated at 36psi max. 
not 50. Too bad I didn't notice when I pumped it to 44psi during a highway 
run, it lasted about 100 miles, then blooey... gone! Bet VW saved maybe a 
buck on the total cost of my vanagon that way, cost me $120Cdn at the time. 
Grrr.   bye tim s.