Every tyre sidewall shows information about the manufacturer, model, size, and load index.

Here's a summary of the most important information and what it means using the above tyre sidewall as an example:

195 - nominal section width, in millimetres.

50 - aspect ratio, this is the height of the tyre sidewall as a percentage of the nominal section width.

R - radial construction, the most commonly used of three different types of tyre construction (cross ply, radial and bias belted).

15 - diameter of the wheel, in inches.

82 - load index, the maximum load capacity of a tyre when driven at maximum speed.

Overloading a tyre, by carrying more weight than it is designed to or running at a lower than specified pressure can cause heat build up and blow outs. Load indexes for passenger cars usually range from 70 - 110 and the maximum load per individual tyre is shown below:



T - speed rating, a representation of the maximum speed that a tyre can sustain at full load. Common speed ratings are:

• Q - for cars with maximum speeds up to 100mph (160km/h)
  
• R - for cars with maximum speeds up to 105mph (170km/h)
  
• S - for cars with maximum speeds up to 113mph (180km/h)
  
• T - for cars with maximum speeds up to 118mph (190km/h)
  
• H - for cars with maximum speeds up to 130mph (210km/h)
  
• V - for cars with maximum speeds up to 150mph (240km/h)
  
• W - for cars with maximum speeds up to 168mph (270km/h)
  
• Y - for cars with maximum speeds up to 186mph (300km/h)
  
• Z - for cars with speeds over 150mph (240km/h)