Illinois Driving Permit Practice Test

To measure tire tread depth effectively, using a penny is a commonly known method. The principle behind this method is straightforward. By inserting a penny into the tread grooves with Lincoln's head pointing down, you can easily gauge the remaining tread. If you can see the top of Lincoln's head, it indicates that the tread is too worn and the tire may need to be replaced, as it typically requires at least 2/32 of an inch of tread depth for safe driving.

While a tire depth gauge is typically the most precise tool for this purpose, and a ruler can be adapted for detailed measurements, the penny method is simple and practical. It allows drivers to quickly assess their tire condition without the need for specialized tools. Using a quarter is similarly effective but can lead to varying depths when it comes to safety standards. Thus, the penny method remains a quick and accessible way to determine if your tires have sufficient tread depth.