What changes between these markings
The aspect ratio and rim diameter stay fixed. The extra 10 mm of nominal width produces 5.5 mm more sidewall height on each side, so overall diameter increases by 11 mm. The resulting radius change is a geometric value, not a prediction of suspension or body clearance.
With 215/55R17 as original and 225/55R17 as new, nominal diameter changes from 668.3 to 679.3 mm: +11 mm (+1.65%). Nominal section width changes by +10 mm and sidewall height by +5.5 mm per side.
Circumference and theoretical speed
Calculated circumference changes from 2099.53 to 2134.08 mm. Revolutions per kilometer change from 476.3 to 468.59, a −1.62% change. Circumference follows diameter in this circular model; revolution counts move in the opposite direction.
At an indicated 100 km/h, the size-ratio calculation gives 101.65 km/h for the new size. At an indicated 60 mph it gives 60.99 mph. Both examples assume calibration corresponds to the original nominal circumference and ignore existing instrument bias and real rolling deformation.
Keep the comparison direction explicit
The published URL keeps one stable order for this pair. Here 215/55R17 is the original denominator. Reversing the inputs gives a −1.62% diameter change and 98.38 km/h at an indicated 100 km/h. Use Swap in the editable tool to inspect that direction; changing only the sign would be inaccurate.
Half of the diameter difference is +5.5 mm of nominal radius change. It is not a measured ride-height change, and the width difference does not locate the installed sidewall without wheel and product information.
Why this pair has a reference page
An original Yahoo! JAPAN question, shared through carview!, explicitly asks about moving from 215/55R17 to 225/55R17. Its clearance question motivates this comparison, but clearance itself cannot be established from the markings.
The linked manufacturer entries establish the individual size markings. The public discussion establishes an editorial reason to compare them. Neither source role supplies a fitment approval, search-volume estimate, purchase recommendation or universal acceptable percentage. Check complete vehicle and product requirements separately.
Sources and further reading
- AltiMAX RT45 — General Tire
- Question about changing 215/55R17 to 225/55R17 — Yahoo! JAPAN carview!
- Tire glossary — Michelin