What is the diameter difference between 265/70R17 and 275/65R18?

265/70R17 has an overall diameter of 31.61 inches (803 mm). 275/65R18 is 32.07 inches (815 mm). That's a 0.47 inch (12 mm) difference — 275/65R18 is taller.

Will 275/65R18 cause speedometer error on a car fitted with 265/70R17?

Swapping 265/70R17 for 275/65R18 produces a speedometer error of about 1.5%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 60.9 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

265/70R17 turns 638 revs per mile. 275/65R18 turns 629 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

265/70R17 has a sidewall of 186 mm (7.3 in). 275/65R18 sidewall is 179 mm (7.04 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 275/65R18 a safe plus-size upgrade from 265/70R17?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 1.5%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.

Tire size comparison

265/70R17 vs 275/65R18

Overall diameter, sidewall, revs per mile, and speedometer error — 275/65R18 is the taller tire, with a 1.5% speedo delta when swapping.

265/70R17

31.61in

803 mm overall diameter

275/65R18

32.07in

815 mm overall diameter

Diameter Δ

0.47 in

Speedo error

1.5%

265/70R17 revs/mi

638

275/65R18 revs/mi

629

Within the ±3% overall-diameter band usually considered safe for plus-sizing — speedometer and ABS calibration should stay close to factory.

Full spec

Side by side

Metric	265/70R17	275/65R18
Section width	265 mm	275 mm
Aspect ratio	70	65
Wheel diameter	17″	18″
Sidewall height	186 mm	179 mm
Overall diameter	31.61 in (803 mm)	32.07 in (815 mm)
Circumference	99.29 in	100.77 in
Revolutions / mile	638	629

Other comparisons for these sizes

265/70R17 vs 265/65R17 275/65R18 vs 285/65R18

FAQ

Frequently asked

What is the diameter difference between 265/70R17 and 275/65R18?: 265/70R17 has an overall diameter of 31.61 inches (803 mm). 275/65R18 is 32.07 inches (815 mm). That's a 0.47 inch (12 mm) difference — 275/65R18 is taller.
Will 275/65R18 cause speedometer error on a car fitted with 265/70R17?: Swapping 265/70R17 for 275/65R18 produces a speedometer error of about 1.5%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 60.9 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 265/70R17 turns 638 revs per mile. 275/65R18 turns 629 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 265/70R17 has a sidewall of 186 mm (7.3 in). 275/65R18 sidewall is 179 mm (7.04 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 275/65R18 a safe plus-size upgrade from 265/70R17?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 1.5%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.