When is it the right time to replace tires? Per the US Department of Transportation, tires must be replaced when worn to a tread depth of 2/32″ (1.6mm) anywhere on the tread surface.
The PENNY TEST is a very simple and cost-effective way to determine if your tires need replacing. Simply place a US penny (with the top of Lincoln’s head facing down) within the tread void between the ribs of a tire. The tread is the section of the tire that is always in contact with the ground. Ribs are the raised portion of tread; they cover the entire circumference of the tire. If the top of Lincoln’s head disappears into the tread of the tire then your tread depth is above the 2/32″ threshold. If his head does not reach the tread, your tread depth is below 2/32″ tread depth and your tires need to be replaced. The penny test is very easy to do and does not require any technical equipment.
Using a TIRE TREAD DEPTH GAUGE is a more precise way to measure the tread depth of a tire. A tread depth gauge uses a probe that measures the void depth of a tire. There are several examples of tread depth gauges but the most common is a graduated scale probe gauge. It is simple to use and read, the depth is measured in 1/32″ increments. The gauge is placed flat on top of the tread blocks and the probe is pushed down into the void of the grooves in the tire. Once the probe reaches the number corresponding to the tread depth, it can be read on the scale part of the gauge. This number is the depth of the tread. If the number is at or below 2/32″ your tires need to be replaced.