Serious injury may result from tire failure because of under inflation or overloading. When you check tire pressure, make sure there is enough tread on the tire to operate safely and that the tires are wearing normally. All grooves should be visible and deep enough to at least touch the top of Lincoln's head on a penny. Look for even wear. If you see the treadwear warning bars across the tire, it's time to replace that tire.
Bald tires are unsafe.
If some spots on the tire seem to be wearing faster than others, see your service station or mechanic. You could have mis-aligned wheels, worn shock absorbers, or other potential problems. Make sure your wheels are balanced and aligned properly. Never overload your car. Your car and tires are designed to operate safely only up to their load limits.