What changes between these markings
A 10 mm width step at 65 percent changes sidewall height by 6.5 mm. Doubling that gives 13 mm of diameter change. The fixed 15-inch rim contributes the same 381 mm to both entries, so no part of the difference comes from rim diameter.
With 195/65R15 as original and 205/65R15 as new, nominal diameter changes from 634.5 to 647.5 mm: +13 mm (+2.05%). Nominal section width changes by +10 mm and sidewall height by +6.5 mm per side.
Circumference and theoretical speed
Calculated circumference changes from 1993.34 to 2034.18 mm. Revolutions per kilometer change from 501.67 to 491.6, a −2.01% 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 102.05 km/h for the new size. At an indicated 60 mph it gives 61.23 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 195/65R15 is the original denominator. Reversing the inputs gives a −2.01% diameter change and 97.99 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 +6.5 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
A Stack Exchange question directly considers 205/65R15 and 195/65R15 for winter use. TireSpan does not evaluate seasonal grip or that vehicle’s requirements; it makes the dimensional consequences explicit.
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
- Can I downsize from 205 65 15 to 195 65 15 Winter tires? — Motor Vehicle Maintenance & Repair Stack Exchange
- Tire glossary — Michelin