[masraum]

Originally Posted by GH85Carrera

What? So all the people putting bigger tiers on cars are just wasting their money?

There is zero doubt a new 911 is outperform an air cooled 911 in every performance test. 50 years of technology makes way more performance, and those big tires are a major part of it.

Jack Olsen has a great 911 that almost all of the air cooled owners lust after. It is far removed from stock.



If you notice he has tires much bigger than stock on his car. He can almost keep up with many modern 911s. But he has no AC, and it is almost a dedicated track only car.

I had to give up on my 15 inch Fuchs because there simply is no summer performance tire that I can drive on long road trips or in the rain. I bought Euromeister 17s and Michelin PS2 tires. I can promise you I have a TON more cornering grip than before.

Right, but does your car have more traction because it's running 17" wheels with wider tires or does it have more traction because it's got a more modern tire with construction and rubber compounds that provide more traction?

From a static physics standpoint, if you could get the same exact tire in a 225 something 15 and a 275 something 18, and you took the same car with 2 different sets of wheels and put them on the car, the contact patches with the same air pressure would be the same size, and the static friction should be the same. Contact patch size is NOT a part of the formula for frictional force, only the coefficient of friction and the force applied.

But I believe most science/engineering types agree that the traction that you get from a tire is not all down to the force applied times the coefficient of friction. There are other factors at play in how a tire provides grip. The tire carcass deforms and how it deforms and how it contacts the road, and the shape of the contact patch and etc.... all make small differences that add up to big differences.

so, yes, from a certain point of view, a bigger tire isn't necessarily going to mean more traction. Also, a different tire will probably provide different traction, maybe more, maybe less, maybe both depending upon the conditions and setup of the car.