Measuring tyre tread depth is essential for safety and legality. You can easily check the depth using a coin or a dedicated tread depth gauge.
Methods for Measuring Tyre Tread Depth
Knowing how to accurately measure your tyre tread depth helps you determine when your tyres need replacing.
The Coin Test
A common and simple method is the coin test, which can give you a quick indication of whether your tread is above the legal minimum limit.
According to the reference: Take the coin and insert it into the tread grooves on your tyre. The principle is that a specific part of the coin, when inserted, corresponds to the legal limit. If, when you have inserted the coin, you cannot see the outer band of the coin, this indicates that your tyre is above the legal limit of 1.6mm.
Practical Steps:
- Find a section of the tyre tread groove.
- Insert the coin (in the UK, a 20p coin is often used because its outer band is approximately 1.6mm from the edge) into the deepest part of the main groove.
- Look at the coin from the side.
- If the outer band of the coin is hidden by the tread, your tyre likely has more than the legal minimum depth remaining.
- If the outer band is fully visible, the tread depth is likely below the legal limit and the tyre needs immediate replacement.
While convenient, the coin test is primarily a pass/fail indicator for the legal minimum and doesn't provide an exact measurement.
Using a Tread Depth Gauge
For a more accurate measurement, a dedicated tread depth gauge is recommended. These are inexpensive tools available at automotive stores.
Steps with a Gauge:
- Ensure the gauge is set to zero.
- Find a main tread groove on your tyre.
- Insert the probe of the gauge into the groove.
- Push the base of the gauge flat against the tyre's surface.
- Read the measurement indicated on the gauge.
Why Tyre Tread Depth Matters
Adequate tyre tread depth is crucial for:
- Grip and Traction: Deeper treads provide better grip, especially in wet conditions.
- Water Displacement: Treads channel water away from the tyre surface, preventing aquaplaning (skidding on a layer of water).
- Braking Performance: Good tread depth ensures effective braking.
- Legality: Driving with tyres below the legal minimum tread depth (1.6mm in many regions, including the UK) is illegal and unsafe.
Practical Tips for Checking Tread Depth
- Check Multiple Locations: Measure in several places around each tyre, as wear can be uneven.
- Check All Tyres: Don't forget the spare tyre if you have one.
- Look for Uneven Wear: If you notice significant differences in depth across the tyre, it could indicate alignment or inflation issues.
Legal Minimum Tread Depth
| Location (Example) | Legal Minimum Tread Depth |
|---|---|
| UK | 1.6mm (across the central three-quarters of the tread, around the entire circumference) |
| Other Regions | May vary, check local regulations |
Checking your tyre tread depth regularly helps ensure your safety on the road and keeps you compliant with the law.
