A label such as 225/45R17 94W describes far more than diameter. Matching the full specification protects handling, load capacity and system calibration.
Decode the size
225 is nominal width in millimeters. 45 is sidewall height as a percentage of width. R indicates radial construction and 17 is wheel diameter in inches.
Respect load and speed ratings
The load index and speed symbol must meet the manufacturer requirement. Extra Load tires may use higher pressure to carry their rated capacity.
Find the age
The final four digits of the DOT code identify production week and year. Age is one factor; cracks, damage, repairs and storage also matter.
Sources and useful tools
NHTSA tire safety ↗Use this guide as a decision aid.
Specifications and procedures vary. Follow the owner’s manual and use a qualified technician whenever safety or diagnosis is uncertain.