In a message dated 2/28/99 12:57:14 PM Pacific Standard Time, pdooley@GTE.NET
writes:

Hi.  I'm no expert, but I've picked up some info over the years.  For
passenger car tires (those that begin with "P"), go by the ratings on the
sidewall.  "A" is best, and higher is better for the number used for the
mileage rating.  For truck tires (those that say "LT", not "P"), see my
answers below:

> Can a tire's sidewall strength be rated by the number of plies?
The ply rating by itself was the old way to rate strength.  If all plies are
created equal, then just adding plies means more strength.  But all plies
aren't equal, so go by the load rating.  "C" is the bottom, then "D", etc.
"C" used to be always 6 ply, and "D" 8 ply, so "D" still equals an 8 ply
rating in tire shop jargon, even though the actual number of plies may be
less.

>  Is there a standard individual ply strength?
No, the plies differ, that is why the "C" or "D" type rating is used.  The
sidewall will show the load that the tire can carry.  Use the single rating
for the Vanagon, not the dual.

>  What if you had a tire with 10 ultra puny plies?
Then you would have a relatively weak tire.

>  Then my 6 beefy ply tire could actually be tougher.
A tire with 6 thicker plies could actually be as strong as a tire with 8
thinner plies, and run cooler.  The more plies there are, the more friction
and heat with flexing.

>  Anybody know for sure?
Just read those sidewall ratings closely.  There are lots of passenger car
tires with aggressive tread designs and truck-like names, but the giveaway is
the "P" for passenger in the description.  And truck tires use the actual
total height and width measurements in inches (I use 27 x 8 1/2 x 14, "C"
rated).  Normally "C" rated LT tires are adequate for the Vanagon, and "D"
ratings are rare for tires small enough to fit.  Passenger car tires use a
sidewall millimeter height, and a percentage of sidewall height for the width
(235mm x 70% x 14inch).
Roger