mfitz said:
How much difference do you think it will actually make when i switch from stock 195/65-15 Continental's to 225/50-15 Kuhmo Victoracer V700's? By difference I mean how much time off a 60-65 second autocross run? Let me know if you are answering from similar 1st hand experience, anecdotal evidence, or just guessing.
Also, will 225 be too wide to function properly on 6 inch wide steelies?( I know that 225mm is approx 9 inches) Maybe I should ask Clay this one?
R compounds will yield 3-4 seconds improvement over decent street tires on a typical 60 second course, perhaps a bit less when compared to RS615, Z212 or MX and the like. A 225 will work on a 6" wheel, but it is far from optimal--my recent background is in a STS Ford Focus, and some of the HS Focus guys were using the 225/50-15 on their Foci. A 205/55-15 (similar gearing) or a 205/50 (shorter gearing) may be a better choice.
That said, you will learn alot more about driving well going to an uber-street tire like the RS615, Z212 or MX than by jumping into R-comp land, so I agree with the sentiment to suggest that route...and that is based on being a pretty serious autocrosser for about 13 years. R compounds will mask driving mistakes, street tires will amplify them.
The Street Touring classes are a blast, IMO...and I see that you want to do springs anyhow. It would be a good stepping-stone to get into SP if that is your ultimate goal. You can run a 225 in STS and a 245 in STX...and wider is better. If you are going to get wheels anyhow, the 225/50-15 in say a BFG KD is about as big as it gets, otherwise everybody makes a 205/50-15...but maybe look at some 16's and at a 225/45-16 Hankook RS2 Z212 (or the Falken RS615 when/if it comes out).
Dynamically, the 15" wheels are the ticket over the 16"s, but if tire choices are the limiting factor, and they seem to be in this case...at leat expand your horizons on what you consider. I ran 205/50-15 Falken RS215s on my Focus and at almost 2800 pounds, could have used a bit more tire...like a 225/45-15 that doesn't exist in the Street Tire world (but does in the R comp world).
Just food for thought.
Erik B
www.waiautox.org