We have been told for years to use Lincoln's head on a US penny as a measurement for safe tire tread depth. This worked out to 2/32-inch as a standard measurement but that standard may be changing. It's been found the depth is not adequate on slick roads, in emergency stops or difficult traction areas. So if current reports and legislature follow through, you'll be using a quarter instead of a penny to indicate new tires are needed.
Wearbars set at 2/32 inch
Consumer Reports mentions the 2/32-tread depth didn't do well on hydroplaning tests or wet pavement cornering and braking. They are now suggesting that a 1/8" tire-tread is the point where a tire starts to lose its traction. Hydroplaning, snow and wet pavement stopping require more tread depth to be safe. Research into when a tire needs to be renewed indicated a deeper tread depth than the traditional Lincoln's head inserted upside down measurement or 2/32nds of an inch.
Accident and collision reports have shown a marked difference between 1/8 inch tire tread and 2/32nds and this is what is causing the push for new standards.
When researching tire tread, safety tests were done using two V rated all season tires: one set with 2/32nds of tread and the second with 4/32nd. Not only did the deeper tread perform better, but also demonstrated that it's the bare minimum for where a tire begins to loose traction. This means the Lincoln head depth was completely inadequate and collisions and accidents investigations have proven the 2/32nd tread depth is unsafe. More serious accidents occurring with the minimum required tread depth and minimum collision damage occurring with deeper tread.
Note the difference in distance to the edge of the coin in these magnified images of the two coins.
Consumer Reports also indicate that instead of a penny for basic tire tread evaluation by consumers, that possibly a quarter should be used. So, the "new" test to keep your family as safe as possible is to check your tire tread with a quarter by inserting it upside down in the groove between the treads. If you can see the top of George Washington's head, you're over due for new tires.
Now, as a responsible driver, you don't have to take anyone's word for this - just test your tires yourself. Take a good look at the difference between the distance of Lincoln's head and Washington's head from the edge of the coin. Do you really want to be driving on tires with such a small amount of tread left as Lincoln's head suggests? When you look at it this way you may agree with my feeling that even George Washington's tread depth is not much, especially during wet or cold seasons when roads become more treacherous than we're used to in good weather...
New legislature and laws concerning tires and tire safety are in the works. Why not get ahead of the lawmakers for a change? Or do you need a policeman to tell you what's good for you?.
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