Originally Posted by Porschefile
Can't speculate on the first part, but I can tell you 295/30 will have more grip laterally and on accel than 265/35, resulting in faster lap times (assuming on a proper wheel width of course).
If I could fit wider than 275 in the front i'd run 285 or 295 square, but the front can only handle 275 slicks on my 18x10's so I do 275 square on track.
Not sure about this.
As a general rule, for a given inflation pressure, a wider tire will provide better lateral traction at the expense of longitudinal traction.