How to measure tyre wear
Wear indicator, depth gauge, changing colours: An inventory of the various devices used to monitor tyre wear.
On the same topic
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.
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
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 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 tyre
Numerical tread wear indicator on a Nokian tyre
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!
The concept proposed by the Yanko Design agency
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
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, use a 20 pence piece, if you can see the inner ring then your tread depth is around 3mm
Although not to be discouraged, this method lacks precision.
Articles in the same header
- Heat wave: safety tips for your tyres
- After how many years should tyres be changed?
- Spare wheel: don't forget the fifth wheel on the wagon!
- Check your tyres before you go on holiday
- How to identify abnormal wear
- Switch your tyres around at least once a year
- Changing tyres: what's forbidden, what's recommended
- When do I change my tyres?
- Tyre pressure: to be checked once a month
- Tyre balancing and alignment