[pure&simple]

I ran into a guy at my last driver's ed event with two 944s... one has 4 degrees of castor, the other only 2.5. He swears the one with 4 degrees tracks smoother on the street (as would be expected) but also has better grip because you gain camber in the corners (dynamic camber) when you increase castor. Can anyone confirm or deny this theory, or share experiences related to playing with castor?

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[flash]

more castor would tend to make the car more stable at speed, as it would have more of a tendency to return the steering wheel to zero

more negative camber is not necessarily a good thing - these car flex a lot in the lower mounting points, which adds a lot of negative camber under load - there is a point at which too much negative camber results in LESS net contact patch

that is exactly why the lower suspension brace works so well - it reduces the amount of camber change, resulting in more stable and consistent geometry

i have found 3.3 on the left and 3.6 on the right to be good castor settings

take a look at this:

http://www.968forums.com/index.php?showtop...alignment+specs

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[PorscheDude]

Flash, is the left/right difference to account for the weight of the driver?

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[flash]

road crown - most roads are sloped to drain to the right

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[Fox944]

I have been using one of Flash's settings for my car for the last 3 years or so. I'm very pleased with the way the car tracks.


FRONT CASTOR L 3.30 deg
FRONT CASTOR R 3.60 deg
FRONT CAMBER L&R -1.00 deg
FRONT TOTAL TOE 0.08 deg

REAR CAMBER L&R -1.50 deg
REAR TOTAL TOE 0.20 deg

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[pure&simple]

Great, thanks guys!

>> that is exactly why the lower suspension brace works so well - it reduces the amount of camber change, resulting in more stable and consistent geometry

Installed shortly after I purchased the car [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]

>> I have been using one of Flash's settings for my car for the last 3 years or so. I'm very pleased with the way the car tracks.

These look very similar to mine, although I run considerably more negative camber in the front. My specs:
Front Castor: 4 deg (up from 3deg)
Front Camber: -2.0 deg
Front Total Toe: 0 deg
Rear Camber: - 1.5 deg
Rear Total Toe: 0.15 deg

Other than bumping caster from 3 to 4, I've just added higher spring rates in the rear. Would have been nice to change only one thing and drive it, but I needed everything to be done for the event at NJMP this monday and tuesday.

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[flash]

lol - that happens

have fun - shiny side up

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[PorscheDude]

Thanks for the settings Dino.
I still need to get some new castor blocks so I can align my car. Been running the phone dials since I got back from Hershey.

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[pure&amp;simple]

Well, I ended up needing a new steering rack (unexpected), so there was no time for an alignment today. Fortunately, nothing about installing the new rack seems to have disturbed the existing alignment settings - the car still drives great. So now the only setup change is higher rear spring rates.

I'll probably get it aligned again before my first fall DE, so I'll post about my findings then.

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[flash]

i have no idea how they could install a new rack and not mess with the toe set - toe set change can easily cause extreme tire wear with no other indication of issue

i'd get an alignment

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[pure&amp;simple]

Well, I'd like to, but I don't know any good alignment shops that work weekends. Event is on Monday. Perhaps I'll get it aligned after the event to see what settings I had.

Pete and Max checked toe with toe plates and total toe is zero which is right where I want it. So if something was out, the car should steer either left or right. With solid bushings throughout, it is extremely sensitive to toe settings. Just a little bit of toe-out and it tries to kill you in highway ruts. Everything feels fine - in fact, even better than before, because there is now more information and more nuance being transmitted through the steering wheel.

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[flash]

unless it is extremely off, incorrect toe will not make the car steer in any direction - that would be a castor thing - toe sets initial turn in and helps to stabilize the car against road change

zero is "ok", though i like to run about 0.1 total, just to keep it from wandering too much

if they checked it after the rack was installed, and it was zero, then you should be fine (assuming they also centered the rack upon install, and got the steering wheel centered by adjusting the tie rods)

and boy do i know what you mean about being sensitive with solid bushings - i have spherical bearings everywhere but the upper strut mounts - very touchy to alignment settings

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