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90 feet is a huge difference in panic stopping power to avoid hitting someone or something!

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

Lincoln loses to Washington in new test for tire-tread depth

Buried deep in a press release from Tire Rack is a bombshell. No longer is the Lincoln-head penny the true test for replacing your tires. It will now be known as the Washington-head quarter test.

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.




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