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Measuring tyre tread depth

Tread depth

The importance of tread depth

Fast facts: Ways to check tread depth

  • Tread wear indicators are spaced evenly through the main grooves in the tyre tread. If they are flush with the level of the tread, then the tyre must be replaced.
  • If you have a tyre tread depth gauge, insert the probe bar into the groove and push the shoulders flush with the tread. Check the top of the gauge to see the measurement.
  • Place a £1 coin in the groove of the tyre. If the gold border shows above the tread, then the tread is less than 3 mm deep. It's time to replace them.

Your tyres form the essential bond between your vehicle and the ground. The tread grips the road as you drive. But if it's not deep enough, your car loses traction and suffers extended braking times. Shallow tread grooves make it harder to control the vehicle in wet weather and the chance of aquaplaning increases. To ensure your safety, measure the tread depth as part of your regular vehicle maintenance.

Tread is the rubber on the tyre that touches the road. New tyres have an average tread depth of 8 to 9 mm. As you drive, the tread will wear down. A tyre with a tread depth below 1.6 mm lacks grip. Braking distance and vehicle control are impaired. These tyres are not safe for driving and must be replaced.

For safety reasons Continental recommends a minimum tread depth of 3 mm for summer tyres. Winter tyres should have a tread depth of at least 4 mm. They need to be thicker to handle wet, icy, and snowy conditions. Ensure your vehicle is equipped with the correct winter, summer, or all-season tyres.

Tread Wear Indicators

Tread wear indicators, or wear bars, are spaced evenly through the main grooves in the tyre tread. If they are flush with the level of the tread, then the tyre must be replaced.

Several winter tyre models are equipped with winter tyre wear indicators.  If they are flush with the level of the tread, the tyre is no longer suitable for winter driving conditions. In some locations, they may also no longer legally qualify as winter tyres.

Using a tyre tread depth gauge

If you have a tyre tread depth gauge, use it to measure the tread depth. Insert the probe bar into the groove and push the shoulders flush with the tread. Check the top of the gauge to see the measurement. Alternately, a small ruler can be used.

Instead of a tyre tread depth gauge, you can estimate the depth with a £1 coin.

Place a £1 coin in the groove of the tyre. If the gold border shows above the tread, then the tread is less than 3 mm thick. It's time to consider replacing them.

Be sure to check in various locations. A misaligned wheel may result in uneven tread wear. Keep an eye open for any areas that look more worn than the surrounding surface. The tyre's tread should be judged by the lowest depth you measured.

If you are uncertain of the measurements, take your vehicle to a service centre. 

Watch for tyre damage

While measuring the tread, look for cupping, or scalloping. These are small scoops, or divots, carved from the tread. They can indicate misalignment or other problems with your vehicle. Take your car to a service centre.

Also, watch out for bulges in the tyre tread or sidewall. They are not safe. You need to get a new tyre.

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