The P205 70R16 tires are significantly narrower than the P255 70R16 tires, which means that they will have less contact with the road. This can affect the vehicle's stability, handling, and braking performance, especially in wet or snowy conditions.
Additionally, the overall diameter of the P205 70R16 tires is smaller than that of the P255 70R16 tires. This means that your speedometer readings will be inaccurate, as the smaller tires will cause your vehicle to travel a greater distance than indicated on the speedometer. This could lead to potential safety hazards, especially if you're driving at higher speeds.
To ensure the safety and proper performance of your vehicle, it is recommended that you use tires with the exact size specified in your owner's manual or by the vehicle manufacturer.