U.S. coins can be substituted for a
tire tread depth gauge as tires wear to the critical final few 32nds of an inch
of their remaining tread depth.
Place a penny into several tread
grooves across the tire. If part of Lincoln’s head is always covered by the
thread then you are still in good shape. You should have around 2/32” of tread
depth left.
Place a quarter into several thread
grooves across the tire. Similar to what you did with the penny. If part of
Washington’s head is always covered by the tread, then you have 4/32” of tread
depth remaining.
According to most states' laws, tires are legally worn
out when they have worn down to 2/32" of remaining tread depth. To help
warn drivers that their tires have reached that point, tires sold in North
America are required to have indicators molded into their tread design called
"wear bars" which run across their tread pattern from their outside
shoulder to inside shoulder. Wear bars are designed to visually connect the
elements of the tire's tread pattern and warn drivers when their tires no
longer meet minimum tread depth requirements.
