The wear of summer tyres and the DSI wear indicator

Back in the old days, various methods were used to try and determine how worn summer tyres were and what their tread depth was – and not all of them were very accurate. Some of the less reliable measurement devices included tread-depth indicators, which could be attached to a key chain, and even two-euro coins. However, these days consumers can rely on the Drive Safety Indicator (DSI) on the surface of Nokian Tyres products, an invention patented in several countries.

Wear indicator, or DSI

  • An indicator on the surface of winter and summer tyres from Nokian Tyres
  • Clearly indicates what the remaining tread depth is for the main grooves in millimetres
  • Helps to swap over the tyres at the right time, thus balancing the wear on the driving tyres and free-rolling tyres

DSI wear indicator

Both summer and winter tyres by Nokian Tyres are equipped with a DSI. Winter tyres include only three numbers – 8, 6 and 4 – while summer tyres with fewer lamellas have a more visible DSI, with consecutive numbering from two to eight at one-millimetre intervals. The DSI is easy to read – the numbers wear off one by one, and the remaining numbers indicate what the tread depth of the tyre is.

Circulating tyres ensures more even wear

We recommend that you check the wear of your tyres regularly. The wear is usually greater on the driving tyres than on the free-rolling ones. To balance the wear on tyres, you should swap the driving tyres and free-rolling tyres around at the right time: when the DSI indicates a wear difference of two millimetres between shafts, the tyres should be swapped. This way, you will finally end up with four equally worn tyres instead of two unusable tyres and two with some useful life left.

The DSI was invented when a clear and easy-to-read indicator was being developed to monitor the wear of lorry tyres. In the past, the wear of lorry tyres was monitored using symbols on the shoulder of the tyre, but the system was not sufficiently clear. Design and product development led to the discovery of how the number of lamellas could be firmly attached to the mould, and the indicator was introduced in winter and summer tyres manufactured by Nokian Tyres. The wear indicator numbers in the surface of the tyre are a sign of a reliable high-quality tyre.


  1. robert kelley says:

    I have been a customer of Fetzer Tire in Southport Ct. I recently complained to Peter Fetzer about tires on 2005 Toyota Tundra needing to be replaced after only 21000 miles. Isn’t there a warranty on your tires? Similar Michelin tires have a 70000. mile warranty! Please advise, other Nokian tires I have purchased have worn much better.I feel this 4 tires are not up to your standards!! Robert Kelley

    • Nokian Tyres' bloggers says:

      Hello Mr. Kelley,
      I’m sorry to hear you feel let down by our product. Please contact Nokian tire professionals in our North American sales office to get information about the mileage warranty issues. Here is their email address or if you prefer to call, the number is 1-800-565-2525.
      – Matti

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