Why are 17 and 18 inch Wheels Considered the best for Performance?

[tyoneal]

To All:

I know this has been brought up offhandedly from time to time, so I thought I would ask it out right.

Why are 17 and 18 inch wheels considered the, "Best" choice for overall performance, (Road Race or Performance Street driving) while larger wheels (> 19 inches, and, < 17 inches) and smaller wheels are generally considered second rate when ONLY handling is considered?

The new Vette and Camaro etc. all have moved to 19 and 20 inch wheels, and at least the Vette is considered one of the finest handling production cars in the world?

Is this just "Old" reasoning, that is now considered out of date or is there some factual reasoning for this that I have overlooked?

Does Staggering the size have any effect one way or the other on the handing of the car, (i.e.. 19 inch in the rear, and 18 inch in the front), or is it just strictly for looks?

I have noticed that many great performing racing cars have a taller, wider tire on the rear and a slightly shorter and thinner tire in the front. (IRL, F1)

Is there any good reason for having the rear of the car higher in the air than the front for a road racing application?

Is it a function of aerodynamics, while under heavy acceleration and "At Speed" running, that the down force will adjust the downward pitch of the car, so while running normally it will move into a nice level stable attitude?

I had heard that depending on the front to back weight ratio of your car, that in some cases this weight differential helps dictate the width of your tires. (i.e.. A car that is heavier in the front than the rear will handle better with a wider tire up front as to help keep understeer to a minimum. While a car with more weight in the back will benefit from a wider rear tire to help reduce oversteer. Is this correct?

Before answering, the drive wheel/wheels should also favor a wide wheel as well.

For instance. A 68 Camaro with 55% of it's weight to the front/ 45% of it's weight to the rear, AND being a Rear wheel drive car. Would benefit from having wide tires in the rear, say 315's (Due to rear wheel drive) and would handle better with front tires being somewhat similar in size as the rear tires, say 295's because the front wheels are having to work harder at changing the direction of the car due to the front being heavier than the rear. (in other words a natural tendency to try and understeer)

This would be one of the reasons, other than weight and aerodynamics, why Drag racers run skinnys up front and as wide as possible in the rear. (Given of course it is rear wheel drive) Changing direction is not an issue so understeer is also a non issue.

Whereas, a rear wheel drive, rear engine car while having 315's in the rear, AND having a weight bias also in the rear could get away with wide tires in the rear and substantially thinner tires up front say 215's without having an undue challenge of dealing with car induced oversteer and understeer.

Is this a correct thought all other influences being static?

Do larger diameter tires as a rule run cooler than smaller diameter tires because the friction of the tread against the pavement is spread out over a larger surface?

I'm sure this is blatantly obvious to most people, but I wanted to clear this up in my mind while giving some thoughts to some project issues.

Thanks for your patience.

Best Regards,

Ty O'Neal