There is no "best" tire for this question. But if you mean "Best" tire width then there is an answer: No wider then 185.
A typical tire size would be 205/70-15
The 205 is the section width 20.5 cm
The 70 means the height of the tire is 70% of the width
The 15 is the rim diameter.
So a 4.5 inch wide wheel is about 11.4 cm wide and a 185 width tire (18.5 cm wide) would be about the widest tire to put on an 11.4cm wide rim.
A typical tire size would be 205/70-15
The 205 is the section width 20.5 cm
The 70 means the height of the tire is 70% of the width
The 15 is the rim diameter.
So a 4.5 inch wide wheel is about 11.4 cm wide and a 185 width tire (18.5 cm wide) would be about the widest tire to put on an 11.4cm wide rim.