Line Follower turning question

hello! my linefollower has 2 wheels, they are 30:1 gear ratio and maximum speed is defined as 255, and minimum is 0. I can also make wheels turn backwards. So what would be the most effective speeds for it to go forward as fast as possible and turn at same time without going off the track? It has 6 sensors that are approximately 15-17cm from motors. Wheels are silicon and their diameter is around 2-3cm

Its accepted practice to use one thread, not three, for questions on the same project - then all the information is in one place.