How to Read Your Tyre Size (AU Guide)
By Tyre On Sale Team·2 June 2026 3 min read
Decoding the sidewall
Every tyre has a code like 225/45R17 91W. Each part means something:
- 225 — width in mm
- 45 — aspect ratio (sidewall height as % of width)
- R — radial construction
- 17 — wheel diameter in inches
- 91 — load index (615 kg per tyre)
- W — speed rating (270 km/h max)
Why it matters
Fitting the wrong size affects speedometer accuracy, fuel economy, and warranty. Always check your placard (driver door jamb) before ordering.
Need help?
Call us or use the Rego Lookup on our homepage — we'll match the exact size to your car.