Understanding Tyre Sizes and Ratings

Before purchasing any tyre please check your manufacturer specifications for the correct tyre for your motorcycle, ATV or UTV.

In the Michelin example above,

As you can see, the sidewall of the tyre shows the following dimensions:
180/55 ZR 17 then:  M/C (73W)

Here is what these codes mean:

  • 180 : The width of the tyre, expressed in millimetres.
  • 55 : The aspect ratio (the sidewall height as a proportion of the tyre width).
  • ZR : The "R" stands for Radial construction. A "ZR" code refers specifically to radial tyres designed for high speeds.
  • 17 : The diameter of the wheel, expressed in inches.
  • M/C : This code simply means that it is a tyre for motorcycles.
  • (73 W) : The number is the load rating of the tyre and the letter following it is the speed rating. The tables below show what maximum load the tyre is able to bear and at what maximum speed it can be driven. In this example, 73 means that the tyre can carry a load of up to 365 kg. The (W) means that it can be driven over 270 km/h.

    Load Rating

    Tyres designed for heavy bikes are often designated as GT or Reinforced.
      Load Index Kilograms Load Index Kilograms
      43 155 67 307
      44 160 68 315
      45 165 69 325
      46 170 70 335
      47 175 71 345
      48 180 72 355
      49 185 73 365
      50 190 74 375
      51 195 75 387
      52 200 76 400
      53 206 77 412
      54 212 78 425
      55 218 79 437
      56 224 80 450
      57 230 81 462
      58 236 82 475
      59 243 83 487
      60 250 84 500
      61 257 85 515
      62 265 86 530
      63 272 87 545
      64 280 88 560
      65 290 89 580
      66 300 90 600


      Speed Index

      Speed Rating Code Physical Meaning
      F 80 km/h
      J 100 km/h
      K 109 km/h
      L 121 km/h
      M 130 km/h
      N 140 km/h
      P 150 km/h
      Q 159 km/h
      R 170 km/h
      S 180 km/h
      T 190 km/h
      U 200 km/h
      H 210 km/h
      V 240 km/h
      Z 240+ km/h
      W 270 km/h
      (W) 270+ km/h
      Y 299 km/h
      Scooter 100 km/h

       

      Tyre Style

      It is important that the style of tyre you choose reflects the type of riding you will be doing.


      Sports Tyres

      • For maximum dry grip but may have less wet grip than touring tyres
      • Extreme track day tyres may only work if they are warmed to the correct temperature

      Touring Tyres

      • Good for all round road use

      Cruiser Tyres

      • Often designed for heavier bikes

      Adventure Tyres

      • Adventure tyres vary a lot based on the ratio of road to off road use
      • Please choose tyres in this category carefully

      Off Road Tyres

      • Not road legal
      • Vary based on terrain type (Sand, Soft, Medium, Hard terrain)
      • Using a farm bike tyre on a MX racing bike is not recommended 

      ATV Tyres

      • Vary based on terrain type
      • Generally speaking the higher the PLY rating the more resistant the tyre is from punctures and tears.