camber question

[Ace]

I'm an advanced beginner participant in PCA DE's , signed off to go solo now. Getting very comfortable on the track in my car
('02 996 C4S) ... working mainly on heel/toe downshifting and carrying speed thru corners.

I bought my C4S from a guy who had installed H&R spings and put 2.5 deg negative camber on the back wheels. I had the local dealers' service dept. align the car and back off as much of the negative camber as possible to extend tire tread life.

I am now the point where I am installing a short throw shifter and aluminum pedals to help with shifting / heel & toeing.

I am looking for advice on whether I should put negative camber back into the rear wheels to improve handling /cornering. Will I be able to tell a difference at my skill level? How much negative camber should I go with on the rears (2.5 or 3 deg?) What should I do about toe-in adjustment on the front wheels.

I am reading Donohue's legendary book "The Unfair Advantage" and there's a great story about him learning the ropes driving on a track and beginning to understand the impact of camber and toe-in adjustments on a car's performance.

Thanks very much for your advice.

[Tyson Schmidt]

It would require a great deal more information than what you've given, to be able to give you an appropriate reply. The alignment settings are dependant on suspension, tires, and driving style/preference.

Basically, the stiffer the suspension and the less body roll requires less negative camber. But the stickier the rubber the more negative camber, since the g-forces will be higher and thus more body roll and sidewall flex. Yet some tires like more than others due to sidewall construction differences.

In a nutshell, you're going to have to find out for yourself with tire chalk, a temp sensor, and some trial and error. The compromise will also depend on how much percentage of tire wear is caused by street driving versus track driving.
For example, you may only spend 1% of the mileage on the track. But due to the rigors of track driving, that 1% may actually account for 75% of the wear your tires will see. That would mean that leaning the alignment specs toward track driving will actually give you better tire life.

[jluetjen]

The C4S is 4WD too, isn't it? That could be a whole new ball of wax compared to our RWD 911's.

[Ace]

Yes, the C4S is AWD ...

Your comments are very helpful ...

I'm working with a fellow at the local shop on camber settings and he suggested that we use a tire temp sensor to calibrate and improve results ...

[Don Wohlfarth]

I think Porsche has gotten most of the C4 understeer like a pig out with the 996's.
Running regular street tires at de's use ~1.0-1.5 neg. Sidewalls aren't stiff enough to use more. With DOT type R you need a little more, maybe 1.5-2.5 neg depending on brand of tire.
Understand your problem learning to heel and toe. Try ty wraping a piece of wood 3/4 X 1 1/2 X 4 on the gas pedal. If that helps there are kits available that extend the brake pedal to the right and some that raise the gas pedal.
Short shifter isn't going to help a lot with heel and toe. Keep practicing on the street at lower speeds so you aren't rushing everything.
Improve the driver not the car.

[HarryD]

Personally, I have no clue about this stuff but you may want to pose this question at http://forums.rennlist.com, in the racing section. A slightly different crowd, just like here but different.

[hobieboy]

Maybe the easiest as a start is to ask you fellow DE-ers/instructors at the track with the same car, and also get a reference from what the factory recommends (which tends to provoke understeer).

For heel & toe, if you are having difficulty with touching both pedals, Wings Engineering make a great pedal. No drilling & multi-way adjustable. Otherwise, its practice, practice & practice.

[jluetjen]

I would be careful to filter the driving instruction input given that your in an AWD car versus most of us in RWD. Some pieces of advice may still apply (be smooth, hit your apex's, etc. ) but a lot may be very different for your car. As Patrick said, try to find some folks who have DE'd your specific model.

You might want to check at your local Barnes and Noble for the latest issue of the SCCA Mag "Sportscar". It has a fairly lengthy article on driving AWD's on the track and in Solo's (as well as off-road in Rally's). Everything that I've ever read has said that performance driving an AWD car (which I've never done) has a lot in common with performance driving a FWD car (which I have done.) For example, while RWD 911's are fundimentally oversteering cars, AWD cars are inevitably understeerers. Much like a FWD car, I've heard that whatever evil happens in a corner, give it more gas and it will pull itself out. I think that it also affects corner entry techniques.

That being said, I'd go back to my opening point -- I would be careful to filter the driving instruction input given that your in an AWD car and most of us are in RWD. Myself included!

[Ace]

great comments and advice .. thanks a million!

[chrisreale]

Originally posted by Ace
I'm working with a fellow at the local shop on camber settings and he suggested that we use a tire temp sensor to calibrate and improve results ...

That is the most productive tool to use in determining the use of tire area. Listining to people is good, because alot of these guys have experience/knowledge, but a pyrometer is going to tell you exactly what your style of driving is doing with your current set-up. Sounds like you are on the right track (pun intended