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Tires For The 21st Century
Firestone OTR Tire Index
  Firestone OTR Tires  Technical Specifications

Structural Diagram

Off-The-Road Radial Tire
Off-The-Road Bias Tire


The size of each tire is indicated by nominal width and rim diameter in inches and mm. Radial structure is indicated by the letter "R". For some tires the aspect ratio is indicated by percentage.


Radial Tire: 40.00R57, 33.25R35, 445/85R25
Bias Tire: 30.00-51, 45/65-45

Star Rating (SR), Ply Rating (PR) and Load Index (LI) The load capacity of a tire is indicated by the star rating (in case of radial tire) and the ply rating (in case of bias tire). The load index is applied in countries where the ETRTO Standards are used.

Overall Diameter (OD) "Overall Diameter" is twice the section height of a new tire, including 24-hour inflation growth, plus the nominal rim diameter.

Overall Width (OW) "Overall Width" is the width of a new tire, including 24-hour inflation growth, and including protective side ribs, bars and decorations.

Static Loaded Radius and Width (SLR, SLW)

"Static Loaded Radius" is the shortest distance from the axle center to the contact surface of a tire and "Static Loaded Width" is the overall width of a tire, mounted on the approved rim at the specified inflation pressure and placed still and vertically on a flat board, and loaded with the specified load.