If you mean tire tread depth, the minimum is 1.6mm.
Minimum LEGAL tire tread depth is 2/32nds of an inch.
Tire spec in PA is 2/32 of an inch of minimum tread
The minimum tyre tread depth in the UK is 1.6mm.
2/32"
2/32 of an inch
A typical automotive vehicle legal tread depth is 2/32", which isn't much.
In most of the USA, the legal minimum is 2/32 inch.
4/32 nds of an inch
Tire spec in PA is 2/32 of an inch of minimum tread
If you take a Lincoln penny and run it upside down, so that the top of Abraham Lincoln's head is toward the center of the tire in the gap of the tread, the tread should be past the top of honest Abe's head. The minimum legal tread depth under Kansas law is 1/16" KS 8-1742.
The minimum tread depth in New York is 2/32". U.S.- and European-manufactured tires have wear bars or tread wear indicators molded into the tread. There are portions of the tire that are raised 2/32". When the tread wears down so the tires are no longer legal, these portions will form a smooth bar across the tire in several places.