I’m pleased to report that with Stephen's tips yesterday I successfully installed the X73 suspension. Overall the car is 2 cm lower (OEM front lip was 165 mm, now it is 145 mm). Judging by the removal of the stock suspension and the installation of X73, the stock suspension is an afterthought for the US market. The X73 slips in easily and feels like it belongs there. The car looks lower though I still clear my driveway and my gas station curbs without scraping.

I took car for a short drive and my first impression is that the ride is almost as smooth as with the stock suspension but more responsive and with more controlled cornering. I still need to align the wheels in the next couple of days. Any recommendations for a good alignment shop in the San Francisco Bay Area?

I searched for the alignment specs and found somewhat different information:

In February of this year Gert form Carnewal (from whom I bought the X73) posted that the X73 suspension needs to be aligned to RoW Turbo specs:

Front:
Camber USA 0' +/-15'
Camber RoW -30 +/- 15'
max difference left to right 20'

Rear
Camber USA and ROW -1d 25' +/-15'
max difference left to right 15'

More recently Dock (Atlanta) has posted:

From the 996 Turbo repair manual group 44-1 page 2...

X73 alignment specifications.

FRONT

Front Toe Unpressed (total) = +5' +/- 5'
Toe difference angle @ 20D lock = -1D50' +/- 30'
Camber = -45' +/- 15' with a max difference left to right of 20'
Caster = 8D +/- 30' with a max difference left to right of 40'

REAR

Rear toe per wheel = +10' +/- 5' with a max difference left to right of 10'
Camber = -1D40' +/- 15' with a max difference left to right of 15'

Which specs should I use when I go for alignment this week?

Thanks for any comments.

 

Ask for zero toe in the front, a little toe-in in the rear,
(no difference from side to side) and a moderate amount
of negative camber all around. That would be maybe
1.5 degrees in front and 1 degree in the rear.

This will give you decent even-enough wear across the tires,
but give enough negative camber to stick in corners.
If you factually do all your driving on freeways, you could
drop the camber down to 1.0 degrees front and .5 deg. rear.

My two cents. FYI, I care only for cornering, and I run
zero toe in front, a little toe-in in the rear, but I run
2.5 degrees negative camber in the front, and 2.0 in the rear.
I might even go .5 higher all around... Camber adds stick in
corners, but takes away straight-line braking.
Joe

 

I used the Porsche recommended ranges (from the Repair Manual), and these were my actual settings post alignment.

Front:

Camber L/R....-0.4/-0.3 (will probably dial it to a little more negative next alignment)

Caster L/R...+8.0/+7.8

Toe L/R...+0.06/+0.05

Total toe front...+0.10

Steer Ahead...0.00


Rear


Camber L/R....-1.5/-1.5

Toe...+0.18/+0.18

Total toe...+0.36

Thrust angle...0.00


The car drives great!!

 

Slate: Glad the tips worked out for you.

Joe: Wow, those are some serious specs, especially the front camber of -2.5. Just curious, what are your thoughts on running less camber at the rear than front in a car like our Turbos as you've suggested? I've always run more camber in the rear because the front caster automatically dials in dynamic camber the more the wheels are turned.

***

Typically, I'll run .8~1.0 neg camber in front, and 1.2~1.8 neg in rear, depending on the car. I always try to max out caster. For front toe, I usually run 0 to slight toe-out for turn-in. For rear, I usually run zero to slight toe-in. This is for an aggresively driven street car, of course, not track car. My Turbo is my 1st Porsche, as well as my first non-front-engine car. So I'd love to hear some input on what your experience has been.

Currently, here are my specs for my Turbo:

F / R
Camber: -.8 / -1.8
Toe: .04 / .03

 

Hi Stephen, the 996tt is my first porsche too. I am trying to
get as much cornering traction as I can for dry asphalt or
concrete at speeds between 15 and 60.
All cars (excepting race cars with serious aero setups) will
transition from understeer at lower speeds to oversteer at
higher speed. If you want safety and smoothness at 150mph,
your car will necessarily push more at the limit at slower speeds.
For what I'm doing, I'm willing to have a twitchy car at 90 if it
will stick like velcro at 40...
The only reason you'd want less camber in the rear is for power
delivery. Because of the power we have, I would strip the inside
edge of the tires to shreds putting the power down at those
speeds, especially with PSM turned off.
If I were ever to go racing with it, or even serious track days/
driver ed sessions, I'd back off on the camber to regain more
braking...
Max caster is a given (for me), but I was of the impression that
our caster wasn't very adjustable...
Joe

 

Why would left be different from right?

 

Most vendors specify an allowable difference to indicate how
much off it can be before you need to deal with it, but it's not
desirable.
I recall a trick some racers used to do... Ford's alignment specs
allow +- .5 degree toe at the *rear* of a live-straight axle car!
Typically, the only way you can have any of this on a rear wheel
is if the axle is not mounted straight in the frame. This is to give
themselves some slack in assembling/selling non-straight cars,
and to define how damaged a car can be before insurance has to
straighten it etc... Camber was unspecified because you can't
have camber in a live axle.
However, for the particular race classification I am thinking of,
Mustangs had to be within factory spec, so racers would heat up
and *bend* the axle housing, putting significant stress on the
differential gears, so that they might have to be replaced every
500 miles or so, but in the meantime, the car got a little negative
camber and toe-in on both sides, but within spec, for a critical
advantage in corners.
Joe

 

The small difference is well within the specified range, and it's as close as they (the dealer) could align it and have the other settings come out where they are.

The best alignment shop around these parts of Atlanta (they do race preps for Road Atlanta) didn't get my previous Porsche any closer when they did the alignment.

I would also think there is a specified calibration for the machine used for alignments, i.e. it might have an accuracy specification of say 0.05 +/- 0.01.

I can say that the car is very squared away for aggressive street driving.