Most states declare that tires are legally worn out when they have 2/32nd inches or tread or less remaining. American tires have ‘wear bars’ molded into their tread at 2/32nd inches remaining. This gives the driver a clear visual indicator of tire wear. However, 2/32nd inches is a bare minimum. As a safe driver you should check your tire tread about once a month. Each time you check your tires’ inflation is an excellent time to also check the tread depth.
Using a Depth Gauge:
Tire tread depth gauges are readily available at auto parts stores and garages and they are very inexpensive. You need to check the depth at many different parts of the tire to check that the wear is even. Using and reading the gauge is self explanatory. You should have at least 2/32nd or 1/16th tread depth.
Another method is using American coins:
First get a US penny coin (officially called the “cent” coin) and a US quarter coin.
Insert the penny in the tread so you can see the side with the Lincoln Memorial on it. If the top of the Memorial is covered then you have 6/32nd inches tread. Again measure the tread depth at various places in the tread across the width of the tire.
Next take your quarter and insert it in the tread with Mr. Washington’s head pointed down. If the tread covers the top of the President’s head then you have at least 4/32nd inches of tread. Don’t forget to measure across the width of the tire to check for even wear.
Now take your penny again and insert it with Mr. Lincoln’s head pointing down. If the top of Mr. Lincoln head is covered then you have the bare minimum legal depth of 2/32nd inches of tread. And again measure at various places across the width of the tire to check for even wear.
Of course the thinner the tread the more likely you are to hydroplane on a wet road. Since you need a thicker tread to channel the water through and out the back of the tread the deeper the tread the safer you are in the rain.
If you drive in the snow, then 6/32nd inches depth is the minimum. Snow tires generally have thicker a tread than standard all weather tires for this very reason. Also some snow tire will have a second set of wear bars at 6/32nd inches.