Another newbie question.

Ok, I know the size of the tires that came stock on my MCS. 205/45 R17.

205 is the width of the tire in millimeters.
45 is 45% of 205 to equal sidewall height (92.25mm)
R17 is the diameter of the rim.

But what is 7x17"? 17" obviously is the diameter, but I can't figure out what the 7 is.

 

crusher,

Aloha and nice to have you on NAM.

>>But what is 7x17"? 17" obviously is the diameter, but I can't figure out what the 7 is.

You are correct with your assessment on the tire size.
The 17x7" refers to the rim size for that tire.
17" diameter and 7' width for the rim.
This size rim will determine what size tire will fit it from the stock
205/45-17 to various but popular other sizes like
215/45-17 or 215/40-17
while wider tires may fit the rim they will rub on the wheel well especially if the MINI is lowered so most of us stop at 215 width.

A wider tire is possible with a larger rim like 18x7 or 18x7.5.

 

Thanks minihune! Must be getting late for me not to have been able to figure that one out. Width of the rim. Geez!