Date:         Sat, 30 Mar 1996 11:47:02 -0500
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Vdubdude@aol.com
Subject:      Re: Radial tire size for '70 Bus?

Hiya Bob!

The correct metric tire size for your bus is a 185/70R14.  The bus/camper is
a one-ton truck (payload capacity).  These are required to use light truck
tires as a result.  Almost noone in the tire industry realizes or cares about
this requirement.  Therefore, many vans & busses run around on "substandard"
rubber.  Most tires today seem to be  overbuilt so it's a moot point anyway.
 You said that you currently use 195/70R14 tires on your camper AND the
speedometer is reading fast, and you are looking to go to yet a larger
diameter tire???   Listen to this carefully....

When you go to a larger first number you are going to a wider tire.  185
refers to 185mm in tread width.  195 refers to 195mm tread width, etc.   The
middle number refers to the sidewall height in relation to the tread width.
 70 would be 70% of 185  = 129.5mm of sidewall height.  70 would also be 70%
of 195  = 136.5mm of sidewall height.  The difference between the 185 and the
195 70's would be a 14mm difference in overall tire height.  Not much
difference, you say??

Well, let's look at your cooling system.  You have a '71 camper.  Equipped
with a beetle motor.  Your engine has in stock form about 60 horses.  Your
vehicle weighs more than a Corvette containing two NFL players.  Your camper
has roughly three times the frontal area that that same Corvette has.  You
need three times the horsepower to maintain 60 miles per hour than that
'Vette 'cause you're pushing three times the air out of your way.  Your
engine relies on engine RPM to cool itself.  Without keeping the revs up
you'll burn that little type1 motor up tying to scale a mountain.  If you
don't burn it up totally, you'll most likely cause some cumulative damage.

Back to your tire selection.  If your tires are larger in diameter than they
are supposed to be, your engine is not turning the correct RPM thus causing
the engine to run hotter.  Remember, heat is our enemy.  If your speedo is
incorrect, I would suggest getting one from the junkyard, a rebuilder, or
learn how far it is off.  Don't give your engine a task harder (hotter) than
is already has.  It's already doomed to begin with (every engine must be
rebuilt eventually).  It is much cheaper to replace a speedometer than a
motor.  If you go back to the stock tire size, you may find that your camper
accelerates slightly quicker and better up hills & mountains (due to lowered
effective axle ratio), handles better (due to quicker response from lower
profile), not to mention the engine lasting longer from the better cooling.

If you're not going to purchase the light truck multi-ply tires (the are
expensive and hard to find), I would suggest the higher speed rated tires as
they are firmer and reinforced in other ways.  My money is on the Sumitomo
HTR70 185/70 HR14  treadwear 320, traction A, temperature A.  Cost?  about
$80.00 each from the Tire Rack.  I run these on my Vanagon and I love them.
 You may also choose to look locally for this tire.  If a local tire store
doesn't want to sell you this tire for this price, ask them what they have in
this size, with these ratings and is at least H rated?  Watch the salesman
start stammering...

Jim Miller, this also applies to your Vanadiesel.  If anyone wants more
specific info on tire brands and prices just post them on the list and I'll
research them as quickly as I can.

Comments?

Vanagon Ric (not to be confused with that Eurovan Ric)
VdubDude@aol.com