Tires. Checking pressure and tread.
Check tires every month, not only for correct pressure but for irregular wear. Tire pressure drops when the temperature takes a big drop; check tires often in winter. Check pressure only when the car has not been used for 4 hours or more. If it is low, drive slowly to the nearest service station and add air. Use your tire gauge to recheck pressure; air-tower gauges are generally inaccurate.
Checking for wear
To check the tread depth, stick a penny into the tire groove, head first. If you can see the top of Lincoln’s head above the tread rubber, it is less than 1/16 inch deep, effectively bald. On most tires, also look for wear bars across the tread. If they appear, the tread is down to inch.
Rear tires should wear down evenly, and front tires should wear slightly more at the edges (shoulders) than at the center. If you corner hard, front shoulder wear increases.
If the front tires are worn more toward one side (as opposed to the normal extra wear in the shoulders), have the wheels realigned. Rear tires on front-drive cars may develop wear patterns similar to front tires. If so, rear wheels can often be realigned.
If front-tire wear is spotty, have the tires balanced and the suspension checked for looseness. Large flat spots encircling the tread may be caused by hard braking in combination with worn shock absorbers. Flat spots can also be caused by grabbing brakes.
Bubbles or waviness in the side-walls and waviness in the tread indicate internal damage. Such tires must be replaced at once.