#TireDiameter

TTAC Reader DeSoto writes:

Greetings, Sajeev — longtime reader, first time writer, and I enjoy the content your column adds to TTAC! (Woot! — SM)

I recently acquired an all-wheel drive 2014 Cadillac CTS with about 15,000 miles on its factory 255/35 R19 Pirelli P7 run-flat tires. Looking ahead to an upcoming 3,500 mile driving trip, I have concern for the durability/drivability of the run-flats. The CTS is not equipped with any wheel-changing tools (jack, wrench, spare tire/wheel). A spare tire assembly (for the CT6) is available online, but I believe the standard compact spare is too small in diameter to be compatible with the 19-inch wheels on the AWD drivetrain. I prefer the freedom of having the option of changing a tire myself and continuing on my way, rather than waiting hours for assistance. I am thus considering, in order of my current preference: