New Tests Show Need for Greater Minimum Tread Depth

(Akron/Tire Review) Consumer Reports magazine has added its voice to the growing international call for a 4/32nds (3.175mm) minimum tread depth level. Tire Review magazine in North America, Tyresafe in the UK and some tyremakers in Europe have pushed for the tyre industry and national and local governments to adopt new minimum tread depth standards to improve driver safety and reduce lost traction accidents and accident-related deaths.

In its November issue, Consumer Reports stated that the well-accepted “penny test” consumers have been taught to use to check tread depth is inadequate.

“It has long been the standard that tyres are worn out when their tread depth reaches 1/16-inch (or 2/32-inch as found on standardised tread-depth gauges),” CR wrote. “The easiest way to measure this, if you didn’t have a gauge, was to hold a penny upside down in the tread. If the top of Lincoln’s head was visible, you needed new tyres.

“But CR’s tests show that using a penny is too stingy and that most consumers should consider replacing their tyres when the tread reaches 1/8-inch (4/32nds),” the CR story said.

The Consumer Reports story explained that the magazine conducted tread depth tests using two V-rated all-season tyres, one set shaved to 2/32nds and the other to 4/32nds.

“Though performance on dry pavement actually improved a bit, the 1/8-inch tread was notably worse in hydroplaning resistance and in snow,” the story said. “By the time only 1/16-inch (2/32nds) remained, wet-pavement cornering and braking had also dropped. This suggests that when your tyres have less than 1/8-inch of tread left, it’s a good time to start shopping for replacement tyres.”

Taking a page from the penny test, CR now recommends consumers use a quarter. “To gauge tread wear, place a quarter upside down in a tyre groove. The distance from the coin’s rim to George Washington’s hairline is about 1/8-inch. If you see more of his head, consider replacing your tyres.”