> Exactly how do we get from GVWR or GAWR to the Load
> spec of 1609-1652lbs.

To get the load spec, take the highest axle's GVWR and
divide by 2. In your van that would be (3,042 lbs/2)
or 1,521 lbs.

A light truck or commercial tire needs to be rated for
at least that amount. No safety margin is required
since it is being used in the application it was
designed for.

> I know there is a safety margin figured in, but I'd
> like to know specifically how to do the actual math.

The load rating of a passenger car tires needs to be
reduced by 9% (divide by 1.1) for use in a light truck
application.
<http://www.yokohamatire.com/utinstallation.asp>
<http://www.tiresafety.com/size_class/size_nav4b.htm#ptire>

LR      Lbs.    9% derate
93      1433    1303
94      1477    1343
95      1521    1383
96      1565    1423
97      1609    1463
98      1653    1503
99      1709    1554
100     1764    1604
101     1819    1654
102     1874    1704

> My 1990 Syncro Westfalia has the following load
> specifications.

> GVWR LB 5512
> GAWR LB Front 2866 / Rear 3042

If you were using a reinforced sidewall passenger car
tire, it would require at least a '99' load rating,
like the Michelin MXL's and MXT's.
A light truck or commercial tire would require a '95'
load rating.

My camper has a rear GVWR of 2,866 lbs, so it would
require a reinforced sidewall passenger car tire with
'97' load rating and a or a '93' load rating in a
light truck or commercial tire. This info matches the
tire selection shown in the front of the drivers door
jamb.

You can always install a higher rated tire than
specified, but in order to get the higher rating, the
tire manufacturer has to add material to the tire,
making it heavier. What effect this extra weigh will
have on the suspension and handling characteristics is
anyone's guess. Typically lighter tires and wheels are
installed to improve handling characteristics, so
wouldn't heavier ones do the opposite? Bigger isn't
always better.

Good luck,

=====
TJ Hannink
Goldibox - 1987 Vanagon Camper, Wolfsburg Edition
Winter Park, Florida
http://home.earthlink.net/~tjhannink/
http://groups.yahoo.com/group/wolfsburg_campers
http://photos.yahoo.com/tjhannink [Vanagon] Album

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