Originally Posted by mattyvac
If we keep the same rim, and put on a higher profile tire, they would be bigger than the wheel well, and wouldn't have clearance. I think we might have try
a fatter tire on a smaller rim, to keep the same height and overall diameter the same. Let's say with the 16 inch rim and low profile tire it has right now, the overall height of the tire and rim is maybe 24 inches. I need to make sure the overall height of any replacement tire and rim combination does not exceed 24 inches, or it won't fit the car.
This is a good start to play around with tire sizes and how they effect the diameter.
Stock 15" focus wheels came with 195/60-15s.
Stock 16" focus wheels came with 205/50-16s
Stock 16" focus wheels came with 215/45-17 or 205/45-17
All of those combinations should get you close 24" overall diameter, +/- 2%. Those are the most common focus tire sizes and have been used by many a focus driver
If you do go with a 15" tire, a nice consequence is that the tires are generally the least expensive of the bunch