RE: caster and lowering

["Jim Adney" <jadney@vwtype3.org>]

On 2 Jun 00, at 10:37, Jaranson, John (J.W.) wrote:

> Yes, Jim I measured from the center of the beam pivots to the centers of the
> ball joints parallel to the centerline of the vehicle, not along the arm
> since they are angled outboard.

Good, I was thinking of the side view, too, so I didn't even think of 
the outboard angling problem. The outboard angling also makes it 
harder to measure the arm angle!

  I only suggested measuring the upper
> trailing arm angle since it is probably easier to get at for most rolling
> cars.  That said, my beam is off the car and I have very easy access to the
> mounting surface on the pan.  This being a better, more common dimension
> between our cars I will attempt to measure the angle relative to the bottom
> plane of the pan.

If you have this all apart then this is a very good way to go. I think 
there are enough references that we can be certain that VW 
intended it to be level (on average, with average load....) Many of 
these sources suggest that the top of the tunnel is a good 
benchmark for "horizontal." Measuring this way will give you the 
opportunity to measure the ORIGINAL (1962) beam angle, but 
you'll have to measure the assymetric late rubber mounts and 
calculate (and report) the change they produce.

> I will make a drawing of this and post
> it on my website for people to take a look at.

What drawing program do you use? If possible, it would be nice to 
be able to download the file.

> It is pretty clear from the
> drawings I did last night that yes....Keith has been right all
> along....caster changes with lowering.....all bow to Keith.  8^)  

For the record, I was skeptical, too. I just hadn't realized how 
totally non-parallelogram the linkage was.

> Now this still does not explain why some of us do not experience severe
> adverse handling effects from lowering.  Obviously, caster is not the only
> factor at work here and all kinds of factors such as CG, shock spring rates,
> tire inflation pressure, etc, etc, etc influence the way a car handles.

Actually I think the answer is clear, and probably not to anyone's 
liking: Our perceptions are grossly affected by our expectations.

If you expect the medicine to help the pain, it will.

If you expect the Monster cables to improve the sound, they will.

If you expect porting your heads going by the seat of your pants to 
improve your engine performance, it will.

If you expect lowering to bring lots of improvements and no 
problems, that's exactly what you will find.

All these facts are the reason that real world tests don't rely on 
subjective perceptions of biased parties. If you want the facts you 
need either objective data, or perceptions of a large sample of 
unbiased people taken in a double blind test.

The medicine folks do this.

The Monster cable people decline.

The head porters blame their losses on other things.

NONE of us, myself included, has any data to back up either point 
of view. Until now. From what he has said, it appears that Keith 
has been the sole exception to this, and only John cared enough, 
and realized that he had the tools to attack the problem.

Thanks to John, and Keith.

-
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054

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