Minnesota Blue Card Practice Test

When using the penny test, your tire tread is considered illegal if it is less than how deep?

1. 1/4 inch

2. 1/8 inch

3. 1/6 inch

4. 1/2 inch

The correct answer is: 1/6 inch

The penny test is a common method for checking tire tread depth. To perform this test, you take a penny and insert it into the tread grooves of your tire with Lincoln's head facing down. If you can see the top of Lincoln's head, it indicates that your tread depth is too shallow, which can be dangerous for driving, especially in wet conditions. A tread depth of less than 1/16 inch is generally considered illegal in many jurisdictions because it is insufficient for safe driving—this ensures that tires remain effective at maintaining traction and preventing hydroplaning. Therefore, the option indicating that your tire tread is considered illegal if it is less than 1/6 inch is correct in this context, as it suggests that tread depth below this level is inadequate for safe road use. While deeper tread depths are acceptable, anything less than this specified measurement fails to meet safety standards. Other options presented, like 1/4 inch, 1/8 inch, and 1/2 inch, either exceed the threshold or don't accurately reflect the legal requirements for safe tire tread depth based on the penny test.