ttAmerica RoadsterAWD

I had my car lowered to ROW sport 125mm front (same as RS), and 230mm rear. Took it to RUF in Dallas and followed instruction for alignment from "Porsche 911 Performance Handbook". I have to disagree on his observations ".......these alignment specs will improve the handling without severely affecting tire wear". Bob at RUF warned me that this would happen, but I wanted to follow this book's instructions. Bob was right.

Front
Toe: +25min +5min (total)
Camber: -1deg +/- 10min
Caster: 4deg 25min +/- 15min

Rear
Toe: +15min +5min (each wheel)
Camber: -1deg 15min +/- 10min

The car is unstable when driven on straightaways. It seems much easier to steer into turns and long sweepingturns, but when traveling straight at speeds, it wants to dart side to side requiring constant correction. It's almost work!

Anybody have any good alignment specs that doesn't take the pleasure out of driving on regular streets? What's your alignment specs and how do you like it?

ps. running JIC/Cross coilover suspension tuned for my cars weight and hp specs.

Jaime

Christer

I run the same settings and I guess the car is a little 'active' on poor road surfaces. I would just decrease the negative camber if you don't likeit - say to 0.5 deg front and rear.....

fstockcarrera

Jaime
Set the front toe to slight " toe in" (factory spec) and your car will not dart on the straight. I run zero front toe for road racing. "Toe out" is too twitchy for me. Toe affects the initial turn in. Your car will still feel the same in sweepers. I don't think the camber is really the problem. Neg camber is why it feels good in the corners. -1 neg is not that much to run on a street car. But the tires will wear slightly fast.
Bob Scotto
1990 carrera cup

ttAmerica RoadsterAWD

Hi Christer, and fstockcarrera. Yeah, Bob said the toe -out will improve turning, but will also twitch. I'm going back to get a slight toe-in and keep the camber. Do our cars have the so called kinematic toe in the rear?, and if so, is there a "rule" that back camber should be .5deg higher than front or something like this? Anyone??

Jaime

Colin 90 C2

Hi Jaime,
Believe it or not, but the toe spec is the same for the C2/4 and the Carrera RS, both front and rear.

The camber is the only spec that is different.

With that being said, I agree with Bob on changing the toe setting. A toe out setting will make the car seem to want to follow any imperfections in the roadway.

I just had my car aligned to RS specs on Friday, but have not really had a chance to drive.
I will try to check it out tomorrow.

I am also fighting with new tires that seem to be very slippery. I have read in the wheel forum that I will need to put a couple hundred miles on them to wear off the mold release agent.
If you put on new tires, this may be compounding your problems.

Please keep us posted.

fstockcarrera

Even in road racing front and rear camber are greatly affected by tire type and character. For me on the street =.5 more in the front. No kninematic toe that's 993. Camber will make the car more reactive to steering input. Bob Scotto

ttAmerica RoadsterAWD

Hi Colin....are you sure the only difference is the camber?? I was under the impression that non RS toe-in was opposite of the RS and less negative in the camber.

I'd be very interested in how you car behaves with the RS alignment. If you get a printout of your alignment, compare itwith the above specs which were obtained from "Porsche 911 Performance Handbook". Let us know how you like it.

Jaime

fstockcarrera

Hi guys. I hate to say this but there is nothing magical about the rs Alignment. Consider that I run on a Carrera Cup -3.4 ft and -2.8 rear with Zero Toe front and 15 min toe in rear(stock), no darting @ 145 mph. Everything else is a comprimise for tire wear on the street. More camber=better cornering with more tire wear. Your choice. The rs spec are a mild improvement of what can had. I would lose the toe out in the front. Use the camber ratio's above and pick your poison.
Bob Scotto

joey bagadonuts

I think Bruce Anderson should reimburse you for the work. Not because his information is wrong but because it's unclear. I don't think it's a huge leap to assume that the specs above are for toe-in measurements and should be stated as: Front +25min +/-5min (total); Rear +15 min +/-10 min (each wheel).

If your car has toe out all around, yes, it should be a handful to drive at speed. If you give Fred Puhn's book a read, How to Make Your Car Handle, you'll not that one of his first statements is that most cars run with a little toe in up front and close to zero toe at the rear. Not only does this setup provide high-speed stability but offsets the additional toe out produced by hard braking. Toe out will also produce a fair bit of oversteer when accelerating out of the corners so please proceed with caution.

FWIW, my car runs with toe-in specs of Front 24 min total, Rear 11 min/wheel. At very high track speeds, this is a VERY stable setup and produces a nice, predictable ride. The extra camber, -3 degrees all around, produces some additional tramlining around town but that's a compromise I'm willing to accept.

$0.02

Colin 90 C2

these are the specs from the workshop manual.

I will let you know my driving impressions as soon as the bad east coast weather clears.

Ade - C4 91

Hi Jamie,

Tyres also make a huge difference. I'm running with RS spec settings on lowered Roock suspension (front at -1 camber, 0 toe, 4.25 caster - RS ride height- 17" wheels).

A set of New Pirelli P-Zero's resulted in appallingly evil and unstable handling, but New Continental SportContact2's resulted in stable and crisp with no tram-lining. This setup was tested on with exactly the same settings on the same day.

Ade

ttAmerica RoadsterAWD

Toe, "unpressed" what does this mean? I've heard some shops lift the vehicle, let the wheels dangle then attempt to align. Is this "unpressed"?

Jaime

avorkinn

How much negativ camber is it possible to get on a standard RS Euro car, front and rear, do I need to do any modifications to get it up tp 3,5 both front and rear?

Colin 90 C2

Update..
With the following settings
-1.2 Camber -1.2
3.8 Caster 4.7
.16 Toe .23
Cross camber -0.0
Cross Caster -.9
Total toe 0.39
set back 0.05

-1.1 Rear Camber -1.0
0.18 Rear Toe 0.23
Total rear toe 0.41
Thrust Angle -0.02

The car drives very straight with no discernable tramlining on 17's
I am able to induce oversteer in the corners by modulating the go pedal, otherwise pretty stable.
Turn-in seems good with a hint of understeer.

It seems the RS alignment settings are pretty good for the street.

I did have to wear in the new tires as they were very squirrely for the first hundred miles.

Now the problem is that the H&R springs don't feel still enough for me.
Back to the slippery slope.

Colin

Jaime- from a 928 board, I saw that they suggest strapping down the body with racheting straps to settle the car. I assume from this comment that the unpressed toe would be to just have the car settle on its own. It seems prety strange to me because the 928 specs also call for an unpressed toe. I also read that while a car has downward pressure applied, as in hard braking, the toe will change.

As for the max negative camber, my US version C2 started with about -3.1 front camber and -2.0 rear camber. I pushed out the setting to the most negative camber when I installed the new struts and springs.

Atgani

Jaime


Just a thought, firstly are your wheel offsets suited to RS suspension geometry settings? Maybe you should be considering the figures for 965 Turbo S? not sure if they're different to RS or standard 965 turbo settings, worth a look though. having run three 964 RSs (mostly on the road) they (RS settings) would not be my first choice, unless the car is used on really well made smooth surfaces the RS is hard work( LHD cars came without power steering)
I would also venture to suggest your car( being a cab) is not the ideal platform to expect what amounts to a track biased setup to work consistently,( too much compliance within the body possibly?) The RS ran with what were effectively solid front strut top mounts which although doing nothing for ride comfort, keep the strut top at a consistent/optimum angle. Have you upgraded your mounts when fitting your uprated suspension ? Furthermore the inner mounting point on the RS trailing arms were fitted with large washers to limit axial movement, have you fitted these ?