Nobody seems to really have any sense of what the correct answer is
to this query.

It is important because this might be one of the most advisable
practices for Westfalia and 15 years from now all Westys will be set
this way after everybody wakes up.

Or, what you read below might be utterly bozo engineering.

I have no idea which of these is true.

This query refers to the *ratio* for selecting spring weights to
match weights on the corners, not about other assumptions of the test.

I have weighed the four corners of my Syncro Camper with some
automotive bathroom scales I got.

In an "empty" (*) state (for me) weighs ~5300lbs as follows:

LEFT    RIGHT   LBS.
20%     25%     FRONT
30%     25%     REAR

The weight at the left rear is fairly massive compared to the left
front.... almost a 50% increase in the back left rear vs. the front left.

The right side does not have this weight disparity front to rear, so
the traditional view that the left rear is an evil corner for some of
our vans (especially Westfalias) is supported .

(*) TEST CONDITIONS: About as empty as it will normally ever be for
me; 5,200lbs: plenty of always-take things in the closets, 3.0L H6
engine in the back, tools and winch under the back seat, no water in
the drinking water system, heavy big fiberglass rooftop box on the
roof, heavy tire/wheel combo on the roof, heavy tires on the van,
ride heights at the four corners set at 19.5" (measured center of
axle to metal of fender above), dual batteries up front, 65lbs dead
weight at front drivers seat to simulate some driver weight, heavy
100% duty air compressor (15CFM at 100psi) at left rear, additional
spare tire on swing away carrier at left rear.

In terms of raw numbers, weight distribution is similar to this:

LEFT            RIGHT   LBS.
1092            1316    FRONT
1598            1294    REAR

The question is what to do about this from a springs point of view.

I noticed that car companies are increasingly setting different
springs to be mounted in each of the four corners of the vehicle to
account for different weights of the vehicle at the four corners.

So, I threw a calculator into Excel to see what the matching springs
I would want to use if I assumed a 500 rate spring at the lightest
corner (front left).

The calculator was set to a "unmodified math" or "straight line"
method of doing the calculations, meaning that I let the calculator
determine all the new spring rates without me altering the formula.

I don't know if this is a valid way to do these calculations or if
some "discount" should be applied to the numbers before converting
them into spring rates.

My spring rates at 500 start off deliberately low because the rig is
optimized for off-road driving as opposed to pavement racetrack handling.

In any case the "straight line" method produced the following
suggestion from the calculator for spring rates at each of the corners:

LEFT    RIGHT
500     600     FRONT
700     600     REAR
(numbers provided are spring rates)

A "60%" aggressive plan would yield the following "toned down"
suggestion, where by "toned down" I mean to have only 60% difference
between spring rates of what is suggested by the  "unmodified math"
or "straight line" method. There is no special logic to the 60% plan
except to pick a number out of the air, and not wanting to introduce
as many other odd effects of this plan as would be otherwise
introduced, about which I am not an expert.

LEFT    RIGHT   Spring Rate
500     550     FRONT
650     550     REAR

If anybody has any expertise on this subject or would care to comment
on the wisdom of this approach or some modification of it, I'd like
to hear about it and whether this is a reasonable way to go about it.

In addition, if you can see some reason to choose one plan or the
other, or a specific spring rate at a corner in which there is a
choice, I'm all ears.

If you would set the spring rates to be heavier or lighter in the
front vs. the back, I could also make such an adjustment to the
formulas that derive these numbers.

It is not an interest of mine to redistribute the weight to be more
even than shown in these tables due to the tradeoffs.

You may be asking why the higher weights on the van are in half of an
X pattern front right front to left rear.

I couldn't say!!!!

I did set the ride height at all four corners at 19.5" and it is
possible that the sheet metal of the van is not actually a perfect
measure of body height, and so we should be applying a discount
factor to account for errors in the height of the sheet metal in the
fender lips.

_______________________________________________
Derek Drew
Washington DC / New York
derekdrew@derekmail.com
Email is best normally but...
PHONE: 202-966-7907 (Call the number at left normally)
(alt/cell for diligent calling only): 703-408-1532