When to change your tires

You may have heard about doing the "penny test" to see when it's time to get new tires. Some experts want to toss that coin test in favor of the quarter.
The penny test is simple. Hold a penny so that you can see Abraham Lincoln's head. Now insert Lincoln's portrait, scalp-side down, into a groove in your tire tread. If your can still the top of his head, it's time for new tires.

That works because the distance between the edge of a penny and the top of Lincoln's head is about 2/32 of an inch (in normal speech, that would be 1/16 of inch, but tire treads are measured in 32nds of an inch).

But now some experts advise a more conservative approach. Instead of Lincoln's head on a penny, use George Washington's head on a quarter. That's about 4/32, or 1/8, of an inch. In track tests conducted by the tire Web site TireRack.com, using a quarter instead of a penny resulted in 24 percent shorter wet-road stopping distances.

If you can see Washington's wig, your tires are as close as you'll want to get to being bald.