What changes between these markings
A 10 mm width increase at a 70-percent aspect ratio adds 7 mm to each sidewall. The outside diameter grows by 14 mm with the rim held at 17 inches. Nominal section width grows by 10 mm; the page cannot infer the installed outer edge from that alone.
With 255/70R17 as original and 265/70R17 as new, nominal diameter changes from 788.8 to 802.8 mm: +14 mm (+1.77%). Nominal section width changes by +10 mm and sidewall height by +7 mm per side.
Circumference and theoretical speed
Calculated circumference changes from 2478.09 to 2522.07 mm. Revolutions per kilometer change from 403.54 to 396.5, a −1.74% 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 101.77 km/h for the new size. At an indicated 60 mph it gives 61.06 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 255/70R17 is the original denominator. Reversing the inputs gives a −1.74% diameter change and 98.26 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 +7 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 Ranger5G thread proposes 255/70R17, and the replies explicitly discuss 265/70R17 as another size. This is evidence of a shared comparison discussion, not a claim about search popularity or a direct two-option survey.
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
- Grabber APT — Specifications — General Tire
- Using 265/65/17 or 255/70/17 on a 19' Sport XLT 4x4 Non FX4 — Ranger5G
- Tire glossary — Michelin