The 991 now comes with 20 inch wheels as standard. Wheels grow in sizes every model. 18, 19 and now 20 inches.

Let’s discuss shortcomings versus benefits of large wheels.

For track everyone advises 18's. Why? I would have thought 18’s for street (more comfort and more rubber for potholes) and more direct feel 20’s for track and for high speed highway runs (good asphalt surface). Let’s discuss...

 

Unfortunately the larger wheel size on the 991 Porsche is all about looks and not performance. The aspect ratio of the tires on the 20" wheels are the same as the 19" wheels on the 997.2 with basically the same width tire. Hence you gain no benefit from less sidewall flex as the sidewall height is the same. All you get is more unsprung weight. Porsche needs to keep a minimum sidewall height to protect itself against claims of tire and wheel damage. 18" wheel/tire combos are favored for the track as they weigh less and there are more DOT approved R compound tires in an 18" size for far less money. An 18 wheel/tire will run circles around the same vehicle with 20" using the same aspect ratio. Throw on some 18" R compound tires with 6/32" tread depth and the 20" wheels/tires don't stand a chance (unless your racing in the rain). The more compelling reason for larger diameter wheels is for larger brakes. However you can reach the point of dimishing return as the extra weight of the rotational mass of the larger wheel/tire starts to offset the gain in braking performance and the weight of larger brakes adds to unsprung weight.

As Colin Chapman said "to add speed, add lightness".

 

Perfectly articulated

+1 rep for you