NHTSA | Saftey in Numbers - June 2013 What you can do

Follow the recommended tire pressure in pounds per square inch (psi) for your vehicle. This information is found on the vehicle placard and in your vehicle owner's manual.
Remember that the correct inflation pressure for your vehicle is found on the vehicle placard, not on the tire sidewall.
Understand that tires may lose 1 psi every month.
Know where the TPMS warning is on your vehicle dashboard, if equipped with TPMS, and take action if you receive this warning.
Don't forget to check the inflation pressure in your spare tire as as well as all tires on infrequently used vehicles.
Carry a tire pressure gauge in your vehicle to ensure an accurate reading of tire inflation pressure. Don't rely simply on visual inspection of your tires to determine whether they are underinflated. Download PDF
Check out NHTSA's tire safety brochure: Tire Safety – Everything Rides On It. Download PDF

Check your vehicle owner's manual for specific recommendations for tire replacement for your vehicle. Some tire manufacturers cite 6 years, others recommend 10 years as the maximum service life for tires.
Look at the sidewall of your tire for the tire identification number (TIN). The last four digits are the week and year of manufacture. Some older tires may have the TIN on the inside sidewall.
Don't forget about your spare tire. Just because the tire hasn't been used and the tread is not worn, the tire may be too old to operate safely.
Be aware of tires on vehicles with occasional use – like recreation vehicles, collector cars, community vehicles, and 15-passenger vans – as they are also susceptible to tire aging.
Remember that the effects of tire aging may not be visible, so do not rely on visual inspection for damage to know whether the tire may have degraded over time. Download PDF

Monitor the tread on all tires on your vehicle. Tires are not safe and should be replaced when the tread is worn down to 2/32”.
Look for the treadwear indicators – raised sections spaced throughout the bottom of the tread grooves. When they appear even with the outside of the tread, it is time to replace your tires.
Try the penny test. Place a penny in the tread of your tires with Lincoln's head upside down and facing you. If you can see the top of Lincoln's head, your tire has less than 2/32” of tread and you are ready for new tires.