There are practical limits to running wider and everything is a tradeoff. We look at data a lot and we look at top finishers. What are they doing?
Here in SoCal we have tracks of every configuration, from tight technical 1.8 mile circuits to big sweeping 3rd/4th gear tracks, to 150mph+ super-speedways. I have run a lot with 255 tires up front during testing and rarely do I find a performance advantage. Never on a track with high speed straights above 120 mph. Top speed suffers in my car with 255s up front. With only 170 rwhp I don't think my car easily overcomes the added rolling resistance, windage, and rotational unsprung weight of the larger tires. Add 100rwhp (Cayman R or 3.6L motor) and we might get a different result because hp is king on a long, high speed straight.
So if you want to win your class, consider everything: running weight, RWHP, tire compound, track configuration, rotational weight, windage, rolling resistance, and then begin to make decisions about what your ideal contact patch will look like. Once you make some tire choices, go out and test them to see how well it is working, analyze, readjust. Now you are ready to win.
