Read the size in order
In 225/45 R17, 225 is the nominal section width in millimeters, 45 is the sidewall aspect ratio and 17 is the wheel diameter in inches. R describes radial construction. The aspect ratio is a percentage of width, not a millimeter measurement. A wider tire with the same aspect ratio therefore changes sidewall height.
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Read beyond the size
The load index and speed symbol are separate requirements. Compare them with the vehicle specification as well as the dimensional size. Extra Load markings do not mean you can choose an arbitrary inflation pressure or carry more than the vehicle permits.
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Use the whole specification
Photograph the door placard and both axle tire markings before shopping. Record any factory staggered arrangement. A size matching the wheel diameter can still be wrong for the wheel width, load, clearance or vehicle. Have the fitter verify the complete package.
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- Continental tire markings ↗Reviewed Oct 6, 2026
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