Because I started to fit 18s on my nova. And I also checked out some 19s tires, but the diameter was way to much.
175/65 R14 = 58,3 cm diameter
225/30 R18 = 59,2 cm diameter
The "smallest" 19" tire I could found was 215/35 with 63,3 cm diameter.
But maybe, they used another tire size? That's all...