How to Measure Tread Depth With Coins

A quick tread measure with a coin will tell you if your tire tread is still legally safe.

The legal minimum tire tread depth is 2/32 of an inch. If your tread is at or below this mark, you need to buy new tires. You can measure your tread using a penny or a quarter. Depending on where the tread hits certain coin impressions, you can quickly know if your tires should be replaced or not.

Instructions

1. Place coin in tire tread. You can use a penny or a quarter. Test several areas of tire tread to ensure you get proper results.

2. Make sure you coin is heads-down in tread. For example, you will want the top of the president's head in the tread. The words on the coin should be upside down.

3. Note where the tread hits on the coin. With a penny, the tread needs to cover some of Lincoln's head. If measuring with the flip side of the penny, the top of the Lincoln Memorial should be covered. If you use a quarter, part of Washington's head should be covered.

4. Decode the measurements. Tread touching just the top of Lincoln's head means there is 2/32 of an inch of tread left. This is the legal limit. If your tread is measuring at this level, it is time for new tires.

   Tread touching the top of the Lincoln Memorial indicates 6/32 of an inch of tread, and tread covering part of Washington's head on the quarter indicates 4/32 of an inch of remaining tread. These are safe tread measurements.

Tips & Warnings

• Although the legal tread depth limit is 2/32 of an inch, consider changing your tires before the tread wears to that measurement. The National Transportation Safety Board cautions that in snow or rain conditions, tires with tread at the legal limit are more likely to fail and might not provide adequate tire safety.

References

• Tire Rack: Measuring Tire Tread Depth With a Coin
• Car Care: Tires and Wheels
• National Transportation Safety Board: Lessons Learned From Accident Investigations