"The issue of Sport Z is Spring 2003 page: 22."

really nice Q&A with Peter Brock. But the part about tires was confusing.

"Sport Z: You once said that the best tires for high-performance are skinny tires. Could you explain why?

Brock: We're approaching tires and technology in the wrong direction. Traction is determined by a tire's contact patch. Provided it sticks to the ground it doesn't matter how big the contact patch is. If you increase downforce on the car, you'll increase the coefficient of friction. There's been no way to control that. It only requires 15 horsepower to drive a car at 50 miles per hour. We can improve comfort and traction by going to skinny tires. It takes less horsepower to drive. Computer-controlled aerodynamics is the solution. We can design cars to drive at an aerodynamic coefficient that is 30 percent less, if we go to skinny tires. Unsprung weight is less with skinny tires and inertial weight is improved. The space saved is tremendous."...."On a commute, you hardly ever corner. You want the least amount of rolling resistance. If you can design a car that forces the car to the ground through a corner, you'd have what you need. With skinny tires, you're running around on a 33 1/3 record basically, instead of the palm of your hand. It also helps if you improve the aerodynamics and have less frontal resistance."...." And skinny tires are better in wet weather, since they don't aquaplane. The only reason we have fat tires on cars is the fashion. Until you change the fashion sense, its not going to change."...."But until you have computer-controlled aerodynamics on cars, fat tires will be the fashion. People equate power with fat tires when the opposite is true, but they don't understand that. Skinny tires are also less expensive. When you can match the performance and make the tires cheaper, that's when you'll see change."

383tpimachine wrote:
I was figuring on 295s all around to keep it square. I know 315s will fit out back but I am leery of using a 315 up front with the early offsets and clearances.

I heard running different widths could cause strange driving quarks but I have no real experience with this beyond street driving 275/305 setup.

I was going with the taller rear tires to get the desired mph in 4th I would like to max out on. 3.55 rear gear at 1:1 295/40/18 hits 148 at my max rpm.

BillH wrote:
Quote:

383tpimachine wrote:
I was figuring on 295s all around to keep it square. I know 315s will fit out back but I am leery of using a 315 up front with the early offsets and clearances.

I heard running different widths could cause strange driving quarks but I have no real experience with this beyond street driving 275/305 setup.

I was going with the taller rear tires to get the desired mph in 4th I would like to max out on. 3.55 rear gear at 1:1 295/40/18 hits 148 at my max rpm.

Travis, unless you've had 3-4 years experience on big tracks running 6+ events per year- none of this matters at all.

Changing the width or size won't gain/loose you anything noticable. However, puting taller tires on the rear can easily lead to your tires rubbing the fenders and you going home early. I know this first hand, have sent 2- C4 drivers home after one session because of this safety concern (and they lost their $250 entry fee).

Max. MPH on the straightaway won't be a function of tires and gears, it's a function of how fast you come out of the corner approaching the straight.
And unless you're going to a track with an extremely long straight, you're not going to see 148.

Drive the car with what you have on it and have fun.

383tpimachine wrote:


I learned real quick with autox not to play with street tires. I have a set of 275 r6s already but am looking to change up my setup to need 18 rims. My car is not lowered at all.

The may place I will be at is Texas motor speedway.

383tpimachine wrote:
I underestand what you are saying.

My current set are still good but traction is limited at my current power level and I plan to up it considerably after learning to drive with a 6 speed well.

Once the 275s are gone I do not want to get another set when I can move to what will work better. ie lighter rims and slightly bigger tires.

BillH wrote:
Another note on corner exit traction/tirespin - Most newer drivers feel they have to use 2ond gear in a tight corner on a road course (which makes tire spin easier).
The fact is that there are almost no corners on a roadrace track that need 2ond gear.
If a Corvette isn't pulling hard in 3rd coming out of a corner, your corner speed is too slow (and corner speed comes with seat time).

Even in a Miata, in a hairpin corner, you'll be 3rd.