Your assertions are well founded. The one thing you overlooked is that a wider tire typically has a higher load rating. What this means is that you can run the wider tire at a lower air pressure without risking tire damage. Using your example, a P185/65R14 tire has a load carrying capacity of 1040 pounds at 30 psi. The P225/50R15 is rated at 1209 pounds at 30 psi. The larger tire needs only 22 psi of pressure to obtain a load rating of 1040 pounds. Therefore, using a larger tire lets you run a lower air pressure which consequently increases the area of your contact patch.
