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Why does the Carera have such big Rims? Smaller rims usually give better performance. Is it all just for looks or what? I believe they have 19s front &, 20s rear.



Smaller Rims less weight, smaller sidewall height, and better turning answer.

because it's a fast car

The same reasons you find the same trend on all performance cars shortly, bigger rims usually mean greater performance, while you're right that smaller rims mean less weight, they don't mean smaller sidewall height and better turning.



The current standard wheel is 18" for the Carrera and 19" on the Carrera S. 20" wheels will fit the only Porsche that has been offered from the factory with staggered rim diameters was the Carrera GT, which had 19s and 20s, although it's not in production . All have wider widths in the back than the front.



As stated already, more contact area means better grip. Better grip means more performance. And both going wider also as taller with in general diameter means more contact area. This is where you run foul on the assumption that a smaller rim means smaller sidewalls. if you run a smaller rim and attempt to keep the same in general diameter, then you're really to get much bigger sidewalls. This will mean more sidewall flex and less tread stability and less performance. To go with a smaller rim you could have a smaller sidewall, but that means a smaller in general diameter which will lower gearing and decrease the contact area.



The other key issue are brakes. The size of the brakes find out the minimum rim size that may be fitted. and the big brakes found on high performance cars the Porsche Carrera included have big brakes.



And of course, bigger rims are perceived by most both good, and rich looking. But the major engineering reason behing this is performance.



The one spot you're correct on is that bigger rims weigh more. also, the construction of low profile tires frequently make them heavier than tires just one series taller. This is all unsprung rotating mass, which is one of the worst enemies for performance. The bottom line becomes the particular application putting such big heavy wheels on a 1970 911S could detroy the car',s performance. But on a new Carrera? A car that weighs more than 1/2 a ton more than that older 911S, and has twice the power? Under those situation the sprung/unsprung weight ration is about the same or better than the older car, and the newer car has more than enough power to reimburse for the extra rotating mass also as the torque curve to manage the bigger in general diameter . In this afterward application, bigger means more performance in spite of the tradeoff with the weight.

As already stated, bigger "rims" wheels and tires yield bigger rubber to road contact patches equals better control and performance. The last time I was in a car with just twelveinch wheels in a high wind, I was scared I goed to die each good gust of wind gave us an unexpected lane change.



If you',ve seen a Carrera with different size wheels on the front and back, then you',ve seen a buggered Porsche. Porsche runs the same size wheels front and rear, as do nearly all automobiles The Ford GT is a notable exemption .



Added:

Unsprung weight is important to handling. Many Porsche 911 Turbos have Porsche',s "Turbo Technology" wheels. These have hollow spokes to decrease their weight by about eight pounds per wheel. The spokes are pressure cast, then hightech welded to the other parts of the wheel.