Replacing tires with wider tires.

Since the speed is determined by the turning of the front driver side,(left),on the P 30 the faster the wheel turns the higher speed it will read. If height is same no problem, but if smaller the wheel turns faster, if higher it turns slower. Vertical weight is distributed on the profile of the tire, and lateral movement is controlled by the strength of the sidewall, which is under more stress with wider tires, as road surface is greater. They may ride softer, but that's due to there weakness. This is assuming the tires are the same rating for weight. You have to understand the tire is designed for the vehicle and any changes are possibly not top design specifications and if below are not recommended and above may change many safety factors.