Re: 83 GT Suspension

[Scott Fisher <sefisher@cisco.com>]

Good to meet you, Robert.  I've also got an '83 GT, a little fresher
than yours (113k on the odometer; I've had it for about a month) and
I've likewise been looking into suspension goodies for it.  Fortunately
for me, the previous owner did a lot of work on the infrastructure --
new wheel bearings, CV joints/boots, struts and bushings up front, and a
few other things as well.  And he's a Car Guy, so he did them right. 
I'm enjoying this car immensely, and I'm thinking carefully about ways
to enjoy it even more.

I've played with the suspensions of about, oh, 20 cars, mostly my own
but several friends' as well, for everything from commuter use,
multi-purpose (daily driver plus autocross) and even full-on Production
category SCCA road race preparation.  When you set out to modify the
suspension of a car, you need to ask yourself what you want to end up
with, and then design a solution for that.  This is one of those areas
where it's easy to mess things up, and just as easy to end up with
something you really enjoy.  You just have to think carefully going into
it.

My cut on the '83 GT is that it's a damn fine car just the way it is,
for probably 80 to 85% of the driving I do with it.  I love the way
Audis glide over surface imperfections, but hunker down and stick when
you wind them into a hard corner.  Yes, my wife's Volvo rides smoother,
and my vintage race Alfa GT will launch out of a tight bend harder, but
in the Audi I don't have to try to jump from one car into the other when
the road changes unexpectedly. :-)

So... I'm looking to avoid destroying this compromise, but at the same
time shift it ever-so-gently in the direction of the racetrack: sharper
turn-in, less of that unsettled, floaty sensation on fast transitions,
but without losing the balance and smoothness the car has in the boring
and outright unpleasant parts of my daily commute.  It sounds like
you're after much the same thing, though perhaps with a little more
top-end sharpness at the expense of a little more ride comfort.

How I intend to do this, to give you another way of looking at it, is by
keeping the stock springs and adding high-performance anti-sway bars and
stiffer rear shocks.  The previous owner of my GT did me a few great
favors, one of which is to use Bilsteins when he replaced the front
struts a few months ago, but the rears are still worn and probably OEM
(if not the actual original pieces).  The Bilsteins work really well,
providing good ride comfort with excellent damping in hard cornering;
they really highlight how sloppy the old rear shocks are. 

I may look for adjustable rear shocks, though -- that's a great benefit
on a FWD car, because it lets you tune the rear end's initial roll
stiffness, which has a great effect on the sharpness of the car's
turn-in.  Write back if you need to know why, it makes this message
longer than it already is to explain here...

Here are some of the considerations when you change springs -- they're
not automatically reasons not to change springs, but they're things to
consider when you're planning a new suspension:

1 - Ride height.  On at least one of my previous cars, on which I
changed to lower springs, I changed back to stock about a year later
because the driveway at work was wearing a hole in my downpipe.  As a
side benefit, and on that particular car (M.G. Midget, not exactly a
high-ground-clearance car in stock form), the stock springs and stiffer
front bar provided better handling than the lower, stiffer springs,
because the camber curve was more effective when you started from stock,
and camber was effectively nonadjustable.  

2 - Camber curve.  Should be a non-issue for our cars, if I remember the
geometry of Macpherson-strut cars correctly -- camber gain is linear
with body roll and the strut's change under compression has minimal
effect on it.  If anything it may be beneficial, but make sure the front
suspension isn't set to provide increased *positive* camber under body
roll (apart from that which naturally occurs as the chassis tilts, that
is).  (I don't think it is -- Ferdinand Piech likes driving too much to
dial in *that* much understeer.)

3 - Wheel/tire clearance.  If you slam the car, you reduce the available
wheel/tire clearance, so make sure to measure everything carefully
before you go out and spend two grand on 17 x 8" rims only to find you
can't turn the steering wheel. :-)  

4 - CV joint geometry.  I've never owned a formula car, but I've helped
friends set them up, and the geometry of the half-shafts is critical for
longevity as well as handling.  Since our Coupes basically have the
geometry of a formula-car transaxle that happens to be in front of the
front wheels instead of behind the driver, it's something to research.

5 - Stiffness *all the time*.  You know this, but bear in mind that when
you put in new springs, the car will be stiffer all the time -- over
potholes, over those iron plates they put on the road to cover
excavations, on freeze expansion joints, everywhere.  This may be what
you want, or something you're willing to accept, but it's something to
be aware of.

6 - Haircut.  Out here in California at least, if you want to drive a
car that's really slammed, you have to have a buzz cut.  (I just got my
hair cut *really* short a couple weeks ago, and when friends ask me why
I didn't get it any shorter, I tell 'em it's because I didn't want to
buy a lowered purple Civic with chrome 17" rims and a 4" polished
muffler tip. :-)

All car suspensions are compromises, trading off performance in one area
for performance in another.  What I like -- purely personally -- about
the Audi is that the "window" of suspension performance is so broad: if
you assign a value of 1 to smooth riding on a bumpy road, and 10 to fast
cornering on a race track, the Audi provides excellent coverage through
a window of from, say, 2 to 8.  Given the kind of driving I use the Audi
for, I spend way more time than I'd like down at #1 and #2, and way less
than I'd like up at #8 or #9.  So I'm looking to broaden the window, not
just move it.  That's why I'm planning to keep the stock springs but add
bars, improve the rear shocks, and eventually go to low-profile, +1 or
+2 tires.  But that may well be just what I'm willing to put up with or
trade off.  And who knows, you may have shorter hair than I do. :-)

For some other thoughts on the matter, check out some of these Web
pages:

http://www.tap1.com/tapksb.htm -- this is Total Audi Performance's
specific page on sway bars; they call out the Coupe GT in particular so
we're covered.  (And I could have sworn that a few weeks ago, they
listed prices of these and other goodies...)

http://www.igdc.com/ejfluhr/audi/Tech/Suspension.html -- this is off
Eric Fluhr's Coupe page (itself worth bookmarking,
http://www.igdc.com/ejfluhr/audi/coupes.html).  The Suspension.html link
details removing and reinstalling the suspension on an '86 Coupe,
something you might want to get familiar with.

As you find sources of information, parts, and advice, please pass it on
-- I'm obviously specifically interested in what you learn, since I've
got the same kind of Audi!

Best of luck,

--Scott Fisher