Regarding your PS: The most baffling measurements to me are tires. The diameter is expressed in inches, the width in millimeters, and the sidewall thickness is

Regarding your PS: The most baffling measurements to me are tires. The diameter is expressed in inches, the width in millimeters, and the sidewall thickness is given as a percentage of tread width. So you get 255/40R17 to describe a 17” tire that's 10” wide with 4” sidewalls. (Or a 430mm tire that's 255mm wide with 100mm sidewalls)