Hello SVT: The thought of little difference between 55 and 60 series I will excuse you for your ignorance. The difference in width can vary about 1" between a 205/60/15 & 205/55/15 tire.The rim width for a 205/55/15 tire should be 6.5" to 7.5" ideally.
Using a narrow rim will cause the tire tread to wear at the center quicker.
