Basic Tyre Knowledge
Basic Tyre Knowledge
How to Read Tire Size



❶Nominal section width (mm)
This refers to the width of the tire excluding design and lettering on the sidewall, etc. *Does not include rim guard.
❷Aspect ratio (series,%)
This figure indicates the ratio of a tire’s heigh.
Aspect ratio(%)= Tire height÷tire width×100
❸Construction code
“R” stands for radial structure.
❹Nominal rim diameter (inches)
Refers to the diameter of the wheel rim suitable for the tire. The term “tire’s inner diameter” is also used.
❺Load Index (LI)
An index expressing the maximum load permitted for a tire under established conditions.
❻Speed symbol
This indicates the maximum permissible speed in symbols under established conditions.
❼Speed category (ZR: over240km/h)
❽Nominal outside diameter (inches)
❾Nominal section width (inches)
❿Load Index: Single/Dual
⓫C: Commercial vehicle
Complies with ETRTO(European tire regulations).
⓬P: Passenger car tire
Complies with TRA(North American tire regulations).
⓭LT: Light Truck
Complies with JATMA(Japanese tire regulations) or TRA(North American tire regulations).
Speed symbol

The speed symbol refers to the maximum speed capability of a tire. It is only valid for a tire that is properly inflated and loaded within the limits of the assigned load index.