The Targa Newfoundland registration materials include an outright declaration that you shouldn’t run a tire aspect ratio less than 40. Lower aspect ratios are better for ultimate steering and cornering performance, but we won’t be on a race track. We’ll be on country roads, and in neighborhoods, and on moderate arterials within towns. There are potholes, broken pavement, frost heaves, nooks, crannies, cracks, rough patched places, the lot. Heck, that set of hazards also describes the 3500 miles of US roads between here and St. Johns.

So this project skews the tire-and-wheel formula away from circuits and toward “normal roads”; that is to say, “rally roads”.  We want more sidewall!

The Cayman, even with its large front brakes, can fit 18 inch wheels. Porsche even sells a factory accessory set of 18s, mounted with Pirelli snow tires. Having the specs of that accessory set, I duplicated the wheel widths and offsets onto a set of Made in Spain Braid Wheels. I paid the $376 customs duty with a smile; I’m sure the Spaniards will send me a check soon.

The tires are high-performance all seasons, in the identical sizes of the factory accessory set. The UTOG Treadwear rating is a 540; somehow I doubt we’re going to reach the mileage that that rating usually implies.

Here’s an 18″ front with the all season 45 aspect ratio versus the OE 20″ with a 35 aspect ratio tire.  Mr. Dunlop would be proud.