Tire pressure and tread, from NHTSA
Where to find the right pressure, when to check it, and the tread test NHTSA describes.
Where the right pressure is
NHTSA says your recommended pressure is on the Tire and Loading Information Label on the driver's side door edge or in your owner's manual. It says the correct pressure is what the vehicle manufacturer has listed, not what is listed on the tire itself.
When to check
NHTSA says to check all tires, including your spare, at least once a month when the tires are cold, meaning the car has not been driven for at least three hours.
The TPMS light
NHTSA says that when the TPMS symbol appears on your dashboard, at least one tire is significantly underinflated, and to check the pressure as soon as possible. It says TPMS is not a substitute for regular tire maintenance.
Tread depth
NHTSA says tires "should be replaced when the tread is worn down to 2/32 of an inch." It says to check the tread at least once a month when you check the pressure.
Two ways to check tread
NHTSA describes built-in treadwear indicators: when the tread is level with them, it is time to replace the tires. It also describes the penny test: with Lincoln's head upside down in the tread, if you can see the top of his head, replace your tires.
Rotation and age
NHTSA says to check your owner's manual for how often to rotate your tires. It says the last four digits of the DOT Tire Identification Number on the sidewall show the week and year the tire was made.
Mileage
FuelEconomy.gov says properly inflated tires are safer and last longer, and can improve gas mileage.
This is general information, not mechanical or legal advice. Your owner's manual and a qualified technician come first.
Sources: NHTSA, Tire Safety (TireWise); FuelEconomy.gov (U.S. Department of Energy and EPA), Keeping Your Vehicle in Shape.
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