In a message dated 6/9/2003 3:15:42 PM Mountain Daylight Time,
william.russell@UW-INC.COM writes:

<< I'm heading out on a big road trip and I'm really concerned about making
 sure my baby is in tip top travelling shape.  What should I keep my tire
 pressures at on a 1980 Westfalia with three people plus gear?
  >>

The recommended tire pressures published by the vehicle manufacturer and
usually affixed inside the drivers door somewhere or in the drivers handbook refer
to proper pressures for the suspension and handling of that particular
vehicle.  Note, these pressures usually specify a tire size and apply only to that
particular size. Usually it is permissable and recommended to increase tire
pressure a bit ( 2 to 5 pounds maybe) if driving at sustained high speeds.  I
think, but am not sure, that VW states so in the drivers handbook.  There is a
liability issue here, remember Ford and Firestone, so manufacturers try to keep
their recommendations only to the original type of tire supplied.

The pressures printed on the tire itself refer to maximum safe pressures of
that particular tire and should not be exceeded. Usually noted at maximum load
of the vehicle, but does not speak to the particular type of vehicle and it's
requirements.  Clearly you do not want to select a tire which states a maximum
pressure rating which is lower than the operating pressures published by the
vehicle manufacturer.

Assuming your tires are the proper ones for your vehicle,  I think the
vehicle Manufacturer's pressures should be followed since a big concern is safe
handling of the vehicle. The tires do perform as part of the suspension, absorbing
impacts, etc and maintaining stability when pushed about by wind on  the road.

Low tire pressure is extremely dangerous for sustained high speed driving and
can result in heat build up  and  complete tire failure, sometimes at speed.
That is what I would be most concerned about. All those shredded rubber bits
spread around on the Interstate roads are from exploded tires on 18 wheelers,
usually caused by heat build up.

All The Best

Bob