Tire Rack; Tire Rack recommends replacing the age-old penny test with the new quarter test for tire-tread depth. By: Jake Lingeman on 5/23/2011
For as long as we can remember, we were taught that when you could see the top of Lincoln's head on a penny stuck in your tire tread, it was time for new rubber. That's about 2/32 of an inch. Tire Rack did some tests, with an eye-opening video, on what the difference is between a new tire (10/32 of an inch), a worn tire (4/32) and a completely worn-out tire (2/32).
The control car stopped at 195.2 feet with new tires in the rain. The next test used the same car, but the treads were worn to 4/32 of an inch, about the distance between the top of a quarter and Washington's head. That car took an additional 95 feet to stop on the slick track.
At 2/32 of an inch of tread (the Lincoln-penny test), the car skidded to a stop at a lengthy 378.8 feet, almost 90 feet more than the Washington-quarter tires and 183.6 feet farther than new tires. Maybe more importantly, the last car was still traveling at 44 mph when the Washington-quarter test car stopped.
We're all for car control here at AutoWeek. Now, if Dutch will let us borrow a quarter, we'll be off to check the fleet.
Watch the panic stopping tests being performed.