Seems to be inconclusive. Even the driver is unsure about what conclusion to draw. Nice video, but it didn't really say much in the end.

 

I was a little surprised at the amount of chassis engineering needed when moving to a 19" wheel. Kinda shows how much work a tire does as a handling component. A wheel mod is not simply slapping on bigger rims and calling it a day, at least if you want a real gain in performance.

 

You can easily get same-width tires in 18" and 19" in the size ranges they're dealing with.

In fact, the standard 18" and 19" tire sizes for an '05 911 Carrera are the same widths:
235/40-18 F, 265/40-18 R
and
235/35-19 F, 265/35-19 R

Again, they should have tested same-width 18" and 19" sizes with the same make/model tires, instead of 225/245 18"ers vs. 245/275 19"ers.

Waste of effort, nothing can be determined from the results.

 

I autocrossed three times on 19's, and.....it sucked. It was frustrating to run clean and still be so damn slow....

On winding roads, violent bumpsteer kept me from enjoying country roads.

I ran 19 inch VOLK GT-V's. 19X8 +49 F, 19X8.5 +49 R. Tires were Hankook S1 Evo's 225/35-19, 255/30-19. Front end grip sucked, lots of transitional understeer. It just sucked! I was glad to go back stock, and even happier to get on 17" RE30's.

19's + low low profile tires SUCK

 

^19 seems to be definitely an overkill for S.