RE: low tire pressure warning light
The 50 PSI printed on the side of the tire is simply the MAX the tire is designed to be inflated to, not the pressure recommended for your car. Your tires are DEFINATLY overinflated at 50 PSI, and will wear faster in the center...Proper inflation pressure will vary due to factors like the weight of the car and the size of the tires. Using stock size tires you should use the pressure printed on the car's door sill. If you change the size of the tires, you need to change the inflation pressure. Here is one way to find the proper inflation pressure.
Fine a large, smooth, empty parking lot. Get some chalk, the big fatkind kids use to write on the sidewalk is best but any will work. First, drive around for a while to get your tires up to normal driving pressure. then go to the parking lot and park at one end, scribe several thick lines across your tread in various spots on each tire. Get in and drive in a straight line for about 100 feet, then get out and check the chalk lines. If the lines are more worn at the edges than in the middle, your tires are under inflated. If the lines are more worn in the middle than the edges, your tires are overinflated. If the lines are evenly worn, your tires are at the proper pressure.