Okay, here's the way I look at this whole equation...
First, a few "given" concepts: The ultimate quest is for balance in handling characteristics. Tire compound characteristics are identical front and rear. Contact patch is the ONLY thing that lets the car accelerate, decelerate, and turn. Period.
Given the above, I break the car's handling characteristics down into four distinct, different phases: Braking, turn-in, mid-corner, and corner-exit.
Braking: Weight transfer is biased heavily to the front, relatively equally.
Turn-in: Weight transfer is shifting towards the outside, but is still biased toward the front. The net result is that MOST of the load is borne by the outside front tire, and almost none by the inside rear.
Mid-corner: Weight remains on the outside of the car, but begins to transfer towards the rear.
Corner-exit: Weight continues to transition towards the rear, and as the steering is unwound, also transfers more equally towards the inside.
Without sufficient contact patch up front, the braking phase is compromised. As you begin turn-in, probably still under braking (trail-braking), the outside-front suspension compresses, and rolls over onto the tire. Assuming that you have the correct amount of negative static camber to provide maximum contact patch, the outside-front tire is now carrying an appreciable majority of the car's total load. With insufficient contact patch area, the car will simply understeer towards the outside of the corner. A larger contact patch will necessarily and obviously allow the car to generate higher cornering loads, allowing for higher corner-entry speeds without excessive understeer. Please note that for these two phases of the corner, the rear tires are essentially doing nothing, and could be about as wide as a bicycle tire and still do their job.
Mid-corner, where you start to come off the brakes and roll onto the gas, is the first point where the rear tires begin to do anything. As the weight begins to transfer rearward and reaches neutrality, we can assume that there are equal loads on the two outside tires. Given that the contact patch determines grip, and that the car is experiencing roughly equal weight distribution front to rear (stock static is something like 51%/49%), then at this point, the tire widths themselves will determine whether the car tends to understeer, remain neutral, or oversteer. If you have a smaller contact patch up front, the car will push. Period.
Corner-exit: As you continue to roll into the throttle, and transfer weight towards the rear, the rear contact patch becomes more and more important, in being able to transfer the power down to the track. Assuming that you can't break loose your tires at 65mph in 3rd gear in a straight line, then you probably have enough rear contact patch to begin with.
The trick to engineering a fast car isn't to focus on one specific phase of the corner, but to maximize them all, to the best of your ability. Honestly, the dampers you run, the bars you use, the control arm angles you set up, all focus on controlling the load transfer to maximize grip.
My question then, is WHY would you want to run a narrower tire up front? Smaller contact patches will hurt you under braking, at turn-in, and in mid-corner. The S197 is a wonderfully balanced chassis, weight-wise, that is intentionally compromised by the factory for the sake of the safety of the "average" driver. The "average" driver will panic-stop, and wants the car to go straight, not get all squirrely. The "average" driver isn't used to oversteer, and doesn't know how to correct for it or use it to their advantage. Understeer is safe, bottom line, and that's what sells cars. "My sixteen year old daughter had to panic-stop to avoid hitting a muskrat, and by God, the car was just stable! Well done!" If the theoretical driver above started to have the rear end come around, that car would have looped, and most likely been damaged, if not destroyed.
NOBODY that takes their car out on a road course can be considered the "average" driver! We LIKE controllable oversteer. This allows us to do a lot of things, like rotate the car at corner entry to allow transition to mid corner sooner. It allows us to keep the rear end rotated all the way through corner exit. If we run small tires up front, the car will push, and that rotation won't happen, and we'll be slow.
Now, let's look at the SN95, which DOESN'T have the near 50/50 distribution that the S197 does. For that chassis, front grip under braking and at corner entry is even more important.
Bottom line: More meat is always good, but if you keep it square front to rear, you'll have a more balanced car. The balanced car will be the faster one out on the track...
I'm running 275/35-18 on all four corners, and that's good enough for the TTB points lead in NASA Midwest, as well as a couple of TTU and TTA track records this year...
