Alignment parameters for track...and some street

[mmasse]

My alignment parameters are as follow: 1976 S with widebody and 3.6 engine conversion. Standard suspension with adjustable Koni shocks. No LSD

Front:
Camber = L: -0.18 deg; R: -0.51 deg
Caster = L: 5.32 deg; R: 5.72 deg
Toe = L: 0.09 in; R: 0.10 in

Cross Camber: 0.33 deg
Cross Caster: 0.40 deg

Rear
Camber = L: -0.94 deg; R: -1.11 deg
Toe = L: .19 in; R: .33 in

Is this acceptable? If not, what should I aim for. I would like to induce some oversteering, since i am having an understeering problem.

I am running 8" wheels with 225/40/18 in the front and 10" with 295/35/18 in the rear.

[Wil Ferch]

In my opinion...it would seem that there is too much rear toe-in....both sides. I *hate* specs given to the customer in "inches". Where is this measured? Edge of tire? Edge of rim? These would be two vastly different diameters,and the same "toe, in-inches" number can be "off" by over 100% if this is mis-communicated. Toe should be given in minutes or degrees..which eliminates this as a communication problem .

You will not eliminate the understeer...especially in low speed turns where there is a lot of steering angle cranked-in. Remember...if you eliminate understeer for low speeds, you will be "pucker-factor" neutral or oversteer at high speed when the steering angle is more "straight-ahead" for the same amount of high "G" loads.

You've got considerable "width" bias of tires front-to-rear..almost 70mm wider in rear than front..that will make for more understeer too. a narrower rear tire or fatter front will lessen understeer.

Although "total" grip might suffer ( maybe not)..if you run closer to "zero" camber in the rear...that will also help your understeer. However, if this ends up putting more rubber "squarely" on the surface during a turn...then it won't help. If I had to choose between these two opposite possibilites, I will predict that at the camber your running on the back, any aggressive turning will get the tires more square to the road with what you have, and it will impart understeer. Try closer to zero camber....espeically with fat booties that you have.

- Wil

[dentist90]

Isn't best way to achieve more oversteer to soften up front sway bar while stiffening rear? Adjustable links are best for tweaking these settings. I'm not a racer ( but I play one on empty roads) but with all that meat on the back the line between a nice controlled drift and backing into a wall will be very fine.
An open diff will also make it a bit harder to create oversteer as it will be harder to get both tires to let go under throttle.

[Wil Ferch]

Mario didn't mention sways being adjustable... in my answer I assumed "stock", as he stated.

Wil

[mmasse]

I have installed Carrera sway bars. I believe thay are both 21mm. I still have the stock sway bars in my garage. I could probably installed the stock 18mm sway bar in the front. Would that be ok? I mean to have 21mm in the rear and 18mm in the front?

Thanks

[Wil Ferch]

Smaller front bar would help..but the question is "how much" ??...I would think some basic alignment adjustments would be easier ???

As a "trial"...can you unhook one end of the current front bar ( giving you effectively "no" front bar)...to experiment the effects first ?

- Wil

[mmasse]

the problem is that I have the stock Carrera sway bar which can not be unhook.

I could try taking it out, but is a PITA.!!!

[dentist90]

Originally posted by Wil Ferch

You've got considerable "width" bias of tires front-to-rear..almost 70mm wider in rear than front..that will make for more understeer too. a narrower rear tire or fatter front will lessen understeer.
Although "total" grip might suffer ( maybe not)..if you run closer to "zero" camber in the rear...that will also help your understeer.
- Wil

I totally agree with Wil. Big fat tires on the back are designed to
i) improve traction during hard acceleration
ii) improve lateral traction in turns, ie reduce oversteer
Having neg camber helps to put the outside tire tread more flush to the pavement during cornering, providing max grip. You want this in the front, but not so much in the rear if you are trying to slide your car around.
Having a real stiff sway bar permits less body roll, but also places more lift on the inside wheel. If you are accelerating through a turn there will be a weight shift to the rear of the car = less weight on inside front. Add a stiff sway bar and there is an even better chance of lifting inside front tire. If you try your old 18mm antisway bar you will probably feel more body roll (watch those big front tires for rubbing!) but both front tires will stay in better contact with the road. At least this is how I understand part of suspension tuning. You mentioned you had adjustable Konis... I wonder if running the fronts a bit softer and the rears really firm will make a difference?
As I mentioned before I haven't tracked my car, but I have slid it around some. The 911 with it's light front end, narrower front tires and rear weight bias especially under accel make it rather tricky to throttle steer (exception: lift off throttle steering)