While the legal minimum of 2/32" of remaining tread depth indicates a need to replace tires, should you buy tires even if part of Lincoln's head is covered when using a penny to measure your tire's tread depth? Take a look at "Measuring Tire Tread Depth with a Coin" to see how U.S. coins can be used in place of a tire tread depth gauge.
If you live in an area where you drive on snow-covered roads part of the year, then you may want to consider performance winter tires for your vehicle or replacing your current tires when less than 6/32" of tread depth remains. If snow is not an issue but rainy days are, then new automobile tires are recommended when you have approximately 4/32" of remaining tread depth.
To see how tread depth makes a difference in your vehicle's stopping distance, watch "Panic Stopping: How Much Tread Depth Do You Need?"