RedlineMan

But I never answered the first question...

If the car were a real barge, adding a sway bar "could" indeed help the front tire's tread ride flatter, and therefore increase front grip. However, this is not likely to happen with a Porsche.

I think the best thing you can do to get a better compromise setup is to increase negative camber while leaving the rest of the suspension alone. I have no real experience with 996s, but I gather this is not necessarily easy. Negative camber will likely solve a lot of your understeer problem, save your tires, and allow you to keep the softer street ride.

I'd go after more negative camber. It's porbably the easiest and cheapet solution.

Noel

Jeeva, go back to street tires!!! You have seen how much fun I have with my car on streets. I've done the race tire thing and I have more fun on streets! Just find a cheap set of streets (AVE ES100s or Kuhmo MXs and replace them every 2,000 miles. It will even be cheaper than race tires.

Lowering you car will also help with decreasing roll and you may be able to increase your negative camber too. Have you considered this?

BTW, when I used to autocross a lot about 9 years ago many front wheel drive guys would put larger anti-sway bars in to decrease understeer. I never understood this, but it did work, especially on the VWs.

Sanjeevan

Hi there, How is your new city treating you....I expected to see you at Nelson ledges two wknds. back, that should be close to you, right ? ....Man, I think I am hooked on R's,...it feels so much better, so it's going to be very difficult to get back to streets.

The car as it is barely makes through my driveway, so lowering will be difficult. I guess I could get some sort of a ramp ???. But, I think I am done with big track expenses for the year, next year I may look in to it.

Let me know which 3-day DE you'll be going for next year at Glen, I am hoping to do a couple of events.
Jeeva

fatbillybob

If your set-up is very well balacned have you thought about a simple tuning as oppsed to changing your set-up? For example such as lower the front of your car say 15mm? This will give you more front bite and more negative camber without any actual camber adjustment. Sometimes cars can be very sensitive to very mild changes in chassis rake. If you feel this change to be positve but too mcuh you can back off the change to say 10mm.

MetalSolid

As I understand it, the simplified theory is: during cornering a car that rolls less will transfer less weight from the inside tires to the outside tires. The less weight that is transferred, the more grip that's available. Stiffer suspension, reduces roll, so in theory stiffening the sway-bar at one axle should create more grip during cornering at that axle. But, with stiffer suspension weight transfer happens quicker.

Noel

Nelson is now a bit far for me to travel...especially for Nelson. I may come back next April for the three-day Mid-Ohio event. I will attend the three day Watkins Glen event put on my the Potomac Region next year.

I hear ya about the R tires, they are certainly faster, but it is the slipping around that I enjoy. This is far easier with streets.. and cheaper too.

JCP911S

Not sure reducing "weight transfer" and thereby making the inside tires "carry" more load is the issue... maybe somebody with more tech knowledge can weigh in here, but intuitively it seems that at the same G-load, the weight transfer side to side would be the same irrespecitve of the degree of body roll??? Or said another way.... roll center (geometry) has more impact here than roll stiffness???? (Never could quite figure this out...)

Well set-up cars frequently lift inside tires during hard conering... (especially cars with extreme weight imbalances such as front drivers and 911s) those tires aren't doing Sh*t.

Certainly a suspension that is stiffer laterally has two other benefits... first, a reduction in the change in suspension geometry (such as camber) allowing the car to optimize the performance of the tires, and second, quicker transient response allowing the driver to go from brake to cornering to accelleration faster.

joey bagadonuts

Have you considered a wider front tire? What sizes do you currently run?

Sanjeevan

Thanks to the two books that I've read on tuning ( the thread on impact of weight on braking resulted in me ordering those books), I can say for sure that body roll has no influence on weight transfer. The only four things affect the total weight transfer 1) weight of the vehicle 2) location of center of gravity 3) cornering force (speed and radius of the corner) 4) track width. Springs and roo bars dictate how the weight is distributed and thus play a role in cornering efficiency.

Sanjeevan

Yes,
Stock F 225 R 295, I am running F235 R285

joey bagadonuts

I just tried the Toyo RA-1's (due in no small measure to all the positive feedback, here) and it was a revelation. I had no idea I could enter a corner with so much speed. I even had to alter my driving style similar to how our front-engined counterparts drive: straightline brake, pitch it into the corner and then jump on the gas.

Previously, I used the MPSC's in 225/255; the Toyo's are 235/275. While the rears are actually about the same size, the fronts are very different in shape and offer A LOT more grip (Toyo is on the right). It's definitely worth looking into.

JCP911S

Another factor that (surprisingly) has not come up is the fact that your C4S is all wheel drive. I have no experience driving AWD cars, but I can tell you that in my regular 911 I can pretty much determine whether it will understeer, oversteer, or stay neutral in any given turn based on how I use the throttle.

The old addage about 911 is that you direct the car with the wheel and steer with the throttle. While that may not be quite as exaggerated in later cars, it is pretty much true for every car driven at the limit...

What driving style to use with AWD... I coudn;t even guess, but from what I have heard, it makes it more difficult to get the car to rotate (which is exactly what understeer does)...if that is the case, that definately is a huge factor in determining the car's acutal behavior

Sanjeevan

Understeer is not a big problem with the current set-up, even the corsas helped with it a geat deal...the issue is with the uneven temp. of the front tires because of the lack of camber. It was hotter on the outside 6-10 degrees, but the wear is O.K