Tire Codes Information

Information provided by Jeff Berton

For tires using the P-metric designation (e.g., P245/50ZR16)

Format:

  [Code][Width]/[Aspect][Speed][Construction][Size]

Code:

  P   = Passenger 
  LT  = Light truck  
  T   = Temporary
  LTP = Light truck, personal use

Width:

  Width at widest point, sidewall to sidewall, in millimeters

Aspect Ratio:

   Tire height in mm, measured tread to bead, divided by width above,
   multiplied by one hundred.

Speed ratings:

(The maximum speed the tire can maintain at its maximum load rating)
  Q - 100 mph
  R - 106 mph
  S - 112 mph
  T - 118 mph
  U - 124 mph
  H - 130 mph
  V - 149 mph
  W - 168 mph
  Z - more than 168 mph

Construction:

  R - Radial ply
  B - Bias belted
  D - Diagonal bias

Size:

  The diameter of the wheel the tire is designed to be mounted on, in inches.

Other information:

  Maximum Air Pressure - This is the max pressure the tire is designed to hold 
                         (note this is more than the recommended inflation
                         pressure)

  Maximum Load         - Weight the tire can support

  Load Index           - A code that indicates the maximum weight the tire can
                         carry at its speed indicated by its speed rating

  Construction         - Tells the number and type of plies used in the
                         construction of the tread and sidewall

  DOT Serial Number    - Identifies the plant, manufacturer, and date of
                         production

  Tread Wear Index     - A rating of the tire's resistance to wear.  100 is the
                         reference.  A 250 rating indicates 2.5 times the wear
                         resistance of the reference tire.  This number cannot
                         be accurately translated to mileage.

  Traction Index       - A rating of the tire's ability to stop on wet pavement.
                         There are three grades, A, B, and C, with A being the
                         best.  This index does not reflect the tire's traction
                         performance on dry, snowy, or icy pavement.

  Temperature Index    - A rating of the tire's ability to dissipate and resist
                         heat.  There are three grades, A, B, and C, with A
                         being the best.