Tips and advice to maintaining your tyres - How to measure tyre wear

How to measure tyre wear

Maintaining your tyres Leigh

Wear indicator, depth gauge, changing colours: An inventory of the various devices used to monitor tyre wear.

Professional depth gauge to accurately measure tyre wear Copyright © : All Rights Reserved

Monitoring tyre wear: A safety issue

Good drivers are in the habit of checking their tyres regularly for wear. Indeed, the tread is the only part of the tyre in contact with the road. The quality of the compound and the depth of sipes directly determine a vehicle’s ability to grip the road. 

A worn tyre is more prone to punctures and aquaplaning.  Its braking performance and road holding also decreases with the rate of wear, especially in winter conditions.

A legal wear limit has been defined by European regulations*. The tread wear limit is 1.6 mm of rubber at any point on the tread for summer tyres.

Different techniques to measure tyre wear

Tread wear indicator

This is the most common system. The tread wear indicator is a 1.6mm thick rubber bar usually embedded at the base of the longitudinal grooves. When the tread wears down to this level, the tyre has reached the legal wear limit and must be replaced. Beyond this limit, drivers are breaking the law.

Proof of tyre wearCopyright © : rezulteo

Standard tyre wear indicator

Tyre wear indicators can be located by looking for one of the following marks on the tyre’s sidewall:

  • The TWI acronym (tread wear indicator)
  • The brand logo
  • A triangle

The Michelin tread wear indicator is a small Michelin ManCopyright © : Michelin

On Michelin tyres, a small Michelin Man shows the location of the tread wear indicators in the main groove.  

Certain brands also propose intermediate tread wear indicators. When they disappear, the tyre no longer offers optimal wet performance.

Intermediate tread wear indicator on a Continental tyreCopyright © : Continental

Intermediate tread wear indicators on a Continental tyre

Numerical tread wear indicator

This system consists in engraving a treadwear scale featuring several numbers on the tread. These numbers, indicating the tread depth, disappear as the tyre wears.  Several brands such as Nokian or Matador, have adopted this system.

Numerical tread wear indicator on a Matador tyreCopyright © : Matador

Numerical tread wear indicator on a Matador tyre 

Numerical tread wear indicator on a Nokian tyreCopyright © : Nokian

Numerical tread wear indicator on a Nokian tyre

Changing colours

Two Chinese designers have designed a tyre prototype that changes colour when the tread is worn.  The principle is simple: The inner part of the tyre is fluorescent orange. So, when the tread is worn, the colour appears. Ingenious, but difficult to implement, according to our specialists!

Tyre rubber changes colour when worn Copyright © : All Rights Reserved

The concept proposed by the Yanko Design agency

Depth gauge

Tread wear indicators are a fast way of assessing the degree of tyre wear, but they do not replace the precision of a depth gauge.  This small tool, available at a low-cost in all car centres, can be used to measure the tread depth in various locations around the tyre, in accordance with regulations.  

Professional depth gauge to accurately measure tyre wear Copyright © : All Rights Reserved

Professional depth gauge

A coin. If you don’t have a depth gauge, then place a coin at the base of one of the tread grooves.

  •  With a summer tyre, a 1euro coin is fine: If the stars engraved on the edge are visible, then you need to change your tyre!
  • With a winter tyre, you need to use a 2 euro coin: If the silver outer edge is visible above the groove, then the tyre is worn.

Although not to be discouraged, this method lacks precision.