What changes between these markings
Only the aspect-ratio input changes. Five percentage points of a 225 mm width add 11.25 mm to each sidewall and 22.5 mm to the full diameter. “Five points” means a change from 45 to 50, not a five-percent increase in overall tire diameter.
With 225/45R17 as original and 225/50R17 as new, nominal diameter changes from 634.3 to 656.8 mm: +22.5 mm (+3.55%). Nominal section width changes by 0 mm and sidewall height by +11.25 mm per side.
Circumference and theoretical speed
Calculated circumference changes from 1992.71 to 2063.4 mm. Revolutions per kilometer change from 501.83 to 484.64, a −3.43% 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 103.55 km/h for the new size. At an indicated 60 mph it gives 62.13 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 225/45R17 is the original denominator. Reversing the inputs gives a −3.43% diameter change and 96.57 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 +11.25 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
A VXOC discussion asks about changing between the 225/45 and 225/50 markings on 17-inch wheels. The question motivates a fixed-width, fixed-rim comparison; the replies are not used as a fitment rule.
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
- Tyre size discussion — 225/45R17 and 225/50R17 — VXOC
- Tire glossary — Michelin