Gunter

Camber looks good on my new to me 993 but what about Toe?

Is it supposed to be Toe-out on all 4 wheels?

When toe-specs are indicated as + does it mean that the wheels are pointing out?

Or in?

Thanks.

No HTwo O

Make sure your shop know how to set the kinematic toe on a 993 too. They need to have a special tool.

Gunter

Thanks, I know about the kinematic toe.

The car is not in a shop.

I want to know if the alignment specs call for toe-out settings for normal street driving.

And, when specs are given, does + mean toe-out or toe-in?

Bill Verburg

When the wheels are turned in, toe is positive (+). When the wheels are turned out, toe is negative (-)

Here are the factory specs,


for quicker turn in many of us run 0 front ot even a little toe out, 0 or a little toe in in front is generally best

same in back but I'd stay w/ a little more toe in and not go to 0 or even as much as is used in front.

Gunter

Thanks Bill.

My front wheels are definitally toe-out and that may explain more wear on the inside edge of the front tires.

Bill Verburg

Some of the faster track guys use some toe out in front, but it makes the car darty, I don't like it that way at all

Nobody I know uses rear toe out

D666S

Those assumptions are with 993 Cup standard wheels (55 offset)

But what about with a quite lower offset? What do you use? greater toe-out in the rear? (with RS A-arms, that is, close to zero KT effect).

Thanks,

David

Bill Verburg

As long as the wheels are reasonably close to stock width and the car is a street car and o/s the factory specs do nicely

for track use you will stray far from what the factory street specs are
on mine w 8.5ET54 fronts and 10ET65 rears

Front: 24 1/2"
Toe: .0* total min (total)
Camber: -2.4/-2.2 deg
Caster: 4.6*/4.5*

Rear: 24 3/4"
Toe: .22/.21* in 22' total in
Camber:-2.0/-2.0*
Everything else standard.
KT 2
2953#

I find that this works great on track and is fine for what little street use the car gets also realize that the car has a very stiff suspension and effective lsd which also affects handling

the weak point of this set up is the driver not the car

Stealth 993

Toe out can be VERY dangerous! You should NEVER run toe out in the rear unless you are the only one to drive the car & want to be 100% focused on driving.

Toe out in the front with make the car turn in really fast, but wander going straight, & tramline.
Toe out in the rear will make the car turn in faster then you want to, then snap oversteer if not paying attention. When breaking toe out can make the rear end super light, & want to change direction. Under heavy breaking the back end can change directions & wag. You really got to watch the car.

I would ONLY do toe out on the front, only of you are tracking, or want quick turn in. Toe out in the rear is for Auto-X or AWD cars to get them to rotate.

On my cars I run 0 toe F/R, it's stable, but the steering wheel does not self center when turning.

Bill Verburg

I've found 993s to be very numb wrt self centering it helps a lot to have max available caster(I've never been able to get mine to max spec for caster), RS uprights and monoball tierods.

a little more scrub radius helps too

D666S

Sorry when I say quite lower offset I mean 16 in the rear. I' have very wide arches and using 930 Fuchs wheels.

Stealth, coincidentally my car is a 993 C4 with RS suspension specs. I copied RS geometry specs but car always understeer a lot, I trailbraking quite good but impossible to make it rotate quickly and I don't want to stiff the rear anti-roll bar which produces much of the effects that you described!.

Thanks guys for your quick and help.

David

Hank Cohn

Gunter:

Bill has put up some good information about the 993 alignment and Stealth is right. I don't know anything about drifting or rallying but for street or track you would never put any toe out on the rear of a 993. Toe out on the front is acceptable but somewhat old-school.

I don't know how to link a thread but here is a quote from Chris Cervelli from 2005. I don't know if you know the name but Chris was a very successful Pro 993 RSR racer back in the day, owner of a Porsche shop and extremely knowledge guy about most things Porsche. If you search for some of the key words in this quote you will find the entire thread which is worth reading:

From Chirs Cervelli:
"The main fact about the 993 chassis is that if the kinematic toe isn't set right, everything else you do is going in the wrong direction.

I know exactly ONE shop (besides me) that bothers to set it right. There may be more, but I haven't seen them.

I use the front bar for small adjustments. I almost never adjust the rear bar because at full soft it makes the rear end fell tippy and sloppy. At full hard you either have oversteer at turn in or wheelspin on exit.

The TRG rear bar is 22mm so it is too large for a normal NA 993. 22mm is the right size for a turbo or perhaps a 4wd 993. RS links are really the only possible solution for a PSS9 or similar set up. Once the car is really low you can use stock links again. The correct size is 20mm.

The bars should work well in the middle position if the following conditions are satisfied:

Kinematic toe set right
Remainder of the alignment reasonably correct. No rear toe out etc.
Ride heights nearly correct
Properly designed springs with spring split of 10% stiffer rear. (+/-5% or so)
Normal tire sizing (245, 285)
Functioning LSD
Some effort to trail brake by the driver

I am happy to adjust the front bar one hole either way but if I have to go more than that I look for another change to make.

Here is how to do it wrong, which is how 90% of 993's I see are set up:

Kinematic toe set to max.
Big rear bar, small front bar
Spring split approaching 80%
Front toe out, minimal rear toe.
Huge rear wing
Worn out LSD, since even a good LSD wears out with this setup
Minimal rear camber due to inside tire wear
Front end too low, rear end too high
Complaints that the front tires don't get hot enough

This is a great setup. It tries to spin if you trail brake, and pushes like crazy if you don't. On exit, you get either wheel spin or massive understeer. If you stick with it and push harder, it always ends with snap oversteer. So you have a car that won't enter, won't exit, eats tires, and tries to kill you.

For George--

The commonly accepted principles only work if the car is close to a decent setup. In stock form, the setup is good, except that the roll is so bad that fixing that will net a benefit even if done in the 'wrong' way.

The other thing you touched on is that feel is a big part of this. You are dead correct. With a 911 you have two options, you can set it up so the rear end is friendly and forgiving and slow to react. This gives the driver confidence that he won't suddenly lose the rear. Or you can make the rear end super quick and twitchy, so when you turn in you feel that rear end take a bite and hold it. That gives confidence as well. All the time it take for the rear end to take the bite is time the driver doesn't really feel what the rear end is doing, and that makes him uncomfortable.

I favor the twitchy rear end. I keep pumping it up until the driver complains that the rear end looses grip right a turn in and then back off a little.

Look at a normal 'bus stop' chicane, (Daytona, Watkins Glen). To get through it, the rear end has to take four separate bites, and twice it has to roll all the way thru the range. The slow rear end is going to be out of shape by the third bite, but the fast rear end, if you can hang on to it, will be ready and willing on every bite.

Chris Cervelli
Premier Motorsports"

Hope that helps,
Hank

PS. Bill, I am glad to know you are still around. I recently found a really great '96 993 and am looking forward to some targeted mods. Your car looks great!

Steve Weiner-Rennsport Systems

Hi Hank,

Good to see you here, once again,....

trophy

Hank,

Thanks for posting this, I haven't seen this before and is very informative....

Tell us about your car and proposed mods..

D666S

Thanks Hank, very interesting.