How to calibrate a tyre tread depth gauge

By David Sholicar

A tyre tread depth gauge is a simple tool that lets you check more accurately and thoroughly the wear on tyres versus using the more commonly known 20p coin trick. While using a 20p piece is a good indicator as to when the tyre tread depth has gone below the legal minimum of 1.6mm, it doesn't let you measure the tread depth very easily across the full circumference of the tyre. A tread depth gauge can help you do this, which can identify uneven wear or bumps and damage hidden within the tread when you need to make a more thorough inspection.

checking tyre tread

What is tread depth?

This is the depth of the central grooves that run all along the outer circumference of a tyre. Depending on the brand, such as Pirelli, Bridgestone or Falken, as well as the particular pattern of the tyre, this could include 2, 3 or 4 central treads that need to be measured. The depth is important as this cavity creates the grip between the rubber and the road that keeps you safe during braking and manoeuvres. Additionally, these central grooves often play a key role in preventing aquaplaning, where the wheel runs over water without friction or contact with the road surface, by evacuating water along and out via the channels away from the tread itself to ensure continuous grip with the road.

What is a tyre tread depth gauge?

This device is a simple combination of two pieces of metal, one with measurement markings and one that remains stable on the surface of the tyre. The central piece reaches to the bottom of the tread cavity while the second remains on the outer surface of the tyre, the distance between giving you a measurement of the tread depth. Today, you can also find electronic versions of these, which work in essentially the same way. The difference between these is that the digital display can offer a slightly more accurate reading and precise number measurement, if this is necessary for you. The digital versions often come with dual functionality for checking tyre pressure as well.

How to calibrate a tread depth gauge?

The easiest way to calibrate a mechanical tread depth gauge is to place it on any flat surface. Provided that the measurement section reads as zero, you can safely assume that the tool is calibrated. For digital versions, you'll need to press a zero button to calibrate it when the measurement piece is fully retracted, which will give the same result.

How do I know my tyres have a safe tread depth?

Of course, in our experience, any tool is only as accurate as the person using it. While you can use a tyre tread depth gauge to perform your own checks for the legal minimum depth of 1.6mm, identifying and diagnosing other potential problems with tyres can be more complex. Years of experience tell us that many tyres can be unsafe to drive despite having well above this legal minimum tread depth.

This can be due to bumps or bulges that can be missed in a quick check, or uneven wear that is indicative of a problem with the wheel alignment or suspension rather than just the tyre itself. While a tyre tread depth gauge will give you more accurate information and can be used to check more of the tyre surface, qualified fitters have access to a range of garage tools. They bring a wealth of experience and are better placed to quickly assess if an issue is linked to other problems in the vehicle.

Free tyre and vehicle checks

If you are at all unsure, our tyre professionals offer free tyre checks as well as inspections of your entire vehicle that can be booked easily online. In our experience, this often addresses multiple potential areas by checking the original issue you were concerned about as well as ensuring a quick diagnosis of any unexpected problems that can only be tested in a garage.

Our nationwide network of garages means you can book your free tyre check at a location convenient for you. Qualified fitters will be on hand to discuss any questions you may have and offer impartial advice on how to get the most out of your vehicle, as tyre requirements will be different depending on both the vehicle and the way you ordinarily use it. Why not book via our website or give us a call to arrange a free check today?

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About the author

Article Author Photo
By David Sholicar
David is the National Retail Operations Manager for Protyre. One of David’s areas of responsibility and expertise is dealing with the DVSA and MOT’s for Protyre. As the Authorised Examiner Designate Manager ( AEDM ) David deals with applications for changes to the many Vehicle Testing Stations ( VTS’s) including managing the growth of the Number of MOT testing stations that Protyre operate, allocating MOT tester roles, and monitoring the MOT Test logs to ensure that Protyre MOT standards are maintained as the best in the industry.
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