The Washington Quarter Test versus The Lincoln Penny Test. For many years, the Lincoln penny was the tried and true test to know when to replace a worn tire.
That approach has been updated by the “new” Washington quarter test and accepted by many in the tire industry.
Originally, it was mandated that a tire be replaced when it was worn down to 2/32”, a DOT (Department of Transportation) standard for minimum legal tread depth. For those that understand a tire’s construction, this would put the tread depth equal to the “wear bars” in the tread. That unsafe tire’s got to go!
Basically 2/32” of tread depth could be found in a simple test using the Lincoln penny (it’s 2/32” from a penny’s edge to the top of Abe’s head). If could see the top of Lincoln’s head when you inverted a penny (Lincoln’s head upside down), and stuck it down into the tread, then the tire was completely worn out, unsafe and should be replaced.
NOW ~ THE NEW AND IMPROVED TEST ~ Take a quarter instead of a penny. If it is inserted into the lowest worn slot or groove on the tire face and you can see the top of Washington’s head, then the tire should be replaced. This ‘new’ distance (from the top of George’s head to the rim of the quarter) is 4/32” (1/8” vs. a new tire at 10 or more/32”!). At this tread depth, the tire has lost a significant amount of traction, especially when braking on a wet surface, as proven in several industry tests.
In an article from Auto Week, the safety implications of proper tire tread depth was demonstrated by the folks at Tire Rack, an online tire company. They did tests, with an eye-opening video, on the difference between a new tire @ 10/32 of an inch, a worn tire @ 4/32 and a completely worn-out tire @2/32. Check out the video on their website.
Here’s an excerpt from that article:
[In the tests…} 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 older 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.
The only thing between you and Mother Earth, regardless of how cool, fast and high-tech your car may be, is the contact patch of 4 tires. Don’t you and your family deserve to be on safe tires? At Pride Auto Care, we understand. See us today for all your tire and automotive service needs.