Your current 185 tires will be the best for fuel economy, the wider the tire the more rolling resistance you have.
You are going from P185/75R14's to low-profile 17"s? On what, a 25 year old Buick? Why?????
The narrower the tyre, the smaller the tyre, the lighter tyre wins hands down. The mass is less, the weight is less, the air resistance is less. Next time you write, please capitalize your name and place a diagonal in the sequence of numbers for the tyres. 225/45/17 is standard. As to asking here for such a drastic change going from 14 inch tyres to 17 inch tyres requires professional advice. Beyond fitting issue in the wheel wells, the speedometer shall be affected, the suspension system, the shock absorbers, handling, need to be considered as well. I urge professional attention to this issue. Bye, Taz.
