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Engineering question: design variables for suspension springs...


Another one of my silly thoughts and questions...

I have the 1990 200T. As it is, it is in need of a new set of shocks.
A few weeks ago it just needed 2 new rear shocks, now it feels like
it needs a whole new set of 4. Wobble, wobble, dip, dip. I was thinking
that if I am going to fit new shocks and since my future list of
upgrades includes a set of sport shocks and springs I might as well
go ahead and fit new gas pressured shock absorbers. As a stability
and safety improvement (and not ta menshun dems kool looks!) I thought
a set of lowered and uprated springs would be nice.

I called the Koni, Bilstein and Jamex supplier. Jamex have no
adjustable shocks for the model, but I'm still waiting for the official
word from Holland. They do however have the springs which lower the
car by about 30mm, the total cost for 4 springs is about $285. A while
back when Koni was the big thing on my mind I gave the local supplier
a call. We spent about 10 minutes just trying to figure what  car
we needed to look at and eventually it came down to the early A6
system as a guideline. The Koni was off-car adjustable and the kit
came  with the struts and springs for a whopping $1000. A week ago I
gave a Bilstein supplier a call and got a quote for about $1100 for
35mm lowering springs and non-adjustable shocks. This is all very
pricey for me. Armstrong (or is it Gabriel, I can't remember the
TV ad) make a set of gas shocks, non-adjustable, just normal fitters.
They are about $250 for a set of 4. Jamex told me I can use a set of
normal gas shocks and run the car on lowered springs. Has anyone
heard or used these shocks? Anyone suggest a reasonably priced
manufacturer of uprated and shorted shocks and struts for the 200T?

I also then found out from my Audi mechanic that there is a spring
works in this town. He said I can take my car in and the guys there
will retension and shorten my stock springs. He says the price is
real cheap as well. The problem is that I don't want to mess with the
stock springs, I would like to remove them and keep them for later
refitting if I need to do so for some reason. So the idea would be to
get them to manufacture a set of springs for me. But how does one go
about this? I mean, if it is so expensive to buy Jamex, Bilstein or
other springs then what is so special about them? What is this about
variable rate damping springs? They're the ones that have tight coiling
at the bottom and the open coiling at the top? Anyone running something
like that on an Audi? Do they make them from a special material or
is it the same metal they use to make the stock springs? What about
those springs that seem oval in shape, small ends, but with a bulge
in the middle? If I go to this spring works how do I describe the
set of springs I want? I'm sure someone on this list must know a bit
about making lowering kits. Do I tell them what metal to use, the
length of the spring, how do I specify the tension of the spring
and other damping details? Ideally I'd like to give them the
parameters to make a spring like that offered by Bilstein or some
sort of Koni based thing, so does anyone have spring parameters for
lowering springs for the 200T?

I'm just stumped as to how to go about designing and building a set
of springs to match the same ones other companies provide. The best
thing I can do when it comes to my shocks is to fit standard market
gas shocks from  Armstrong or Gabriel. Hopefully these with lowered
springs will give the setup I want, less body roll, better performance
driving. Basically a compromise between a stiffer sport ride and
this very soft comfy ride these Audis have.

Hope someone on the list can help here. :) Could even manufacture
some QList sport springs to go with all the QList performance mods. :)

"a thousand miles from here, there is another person smiling"
1990 Turbo (200T)
name   : gerard van vught
tel    : +27-57-912 2658 (w) / 082 923 9609 (cell)
url    : http://www.acenet.co.za/homepages/gerard/
e-mail : gerard@poboxes.com  / han.solo@galaxycorp.com
         gerard@acenet.co.za / van_vught@frg.issi.co.za