How to Read Vehicle Tyre Specifications and Markings ?

The sidewall of tyre provides the information about the tyre including the specifications, the brand, etc. All the codes on tyres are standardized and recognized by all tyre manufacturers worldwide
Tyre Specification

Meaning of codes marked on tyres:

  1. Tyre width (in mm)
  2. Aspect Ratio
  3. Rim Diameter (in inches)
  4. Load Index
  5. Speed rating

Specifications of tyre marked on sidewall on above image as 235/45R17 97W
The ‘235’ indicates the section width of the tyre in millimeters.
The ’45’ tells the ‘profile’ of the tyre, or the width of the tyre compared to its height. It is expressed in percentage. (45%, in this case).
The ‘R17′ indicates the size (in inches) of the wheel rim to which the tyre is designed to be fitted.
The ’97’ indicates the tyre’s load index, and
The ‘W’ denotes the speed rating.

Load Index:
Load index corresponds to the load capacity . Commonly chosen load index values of automobiles are shown below in image.
Tyre Load index table

Speed Rating:
The Speed rating of a tyre is the maximum speed at which the tyre can carry a load corresponding to its load index is an assigned letter ranging from J to Z that corresponds to the reference maximum speed at the associated load index. Refer to the speed rating table below.
Tyre Speed rating Table

Vinodh Reddy is an Editor-in-chief of ME Mechanical. He holds Bachelor of Engineering (Honours) degree in Mechanical Engineering from BITS-Pilani.

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