What is the diameter difference between 255/40R19 and 265/35R20?

255/40R19 has an overall diameter of 27.03 inches (687 mm). 265/35R20 is 27.3 inches (694 mm). That's a 0.27 inch (7 mm) difference — 265/35R20 is taller.

Will 265/35R20 cause speedometer error on a car fitted with 255/40R19?

Swapping 255/40R19 for 265/35R20 produces a speedometer error of about 1%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 60.6 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

255/40R19 turns 746 revs per mile. 265/35R20 turns 739 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

255/40R19 has a sidewall of 102 mm (4.02 in). 265/35R20 sidewall is 93 mm (3.65 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 265/35R20 a safe plus-size upgrade from 255/40R19?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 1%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.

Tire size comparison

255/40R19 vs 265/35R20

Overall diameter, sidewall, revs per mile, and speedometer error — 265/35R20 is the taller tire, with a 1% speedo delta when swapping.

255/40R19

27.03in

687 mm overall diameter

265/35R20

27.3in

694 mm overall diameter

Diameter Δ

0.27 in

Speedo error

255/40R19 revs/mi

746

265/35R20 revs/mi

739

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	255/40R19	265/35R20
Section width	255 mm	265 mm
Aspect ratio	40	35
Wheel diameter	19″	20″
Sidewall height	102 mm	93 mm
Overall diameter	27.03 in (687 mm)	27.3 in (694 mm)
Circumference	84.92 in	85.78 in
Revolutions / mile	746	739

Other comparisons for these sizes

245/45R18 vs 255/40R19 245/45R18 vs 265/35R20 255/45R18 vs 255/40R19 245/40R19 vs 255/40R19 245/45R19 vs 255/40R19 255/35R19 vs 255/40R19 255/40R19 vs 255/35R20 255/40R19 vs 275/30R21 255/40R19 vs 265/35R19 245/35R20 vs 265/35R20

FAQ

Frequently asked

What is the diameter difference between 255/40R19 and 265/35R20?: 255/40R19 has an overall diameter of 27.03 inches (687 mm). 265/35R20 is 27.3 inches (694 mm). That's a 0.27 inch (7 mm) difference — 265/35R20 is taller.
Will 265/35R20 cause speedometer error on a car fitted with 255/40R19?: Swapping 255/40R19 for 265/35R20 produces a speedometer error of about 1%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 60.6 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 255/40R19 turns 746 revs per mile. 265/35R20 turns 739 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 255/40R19 has a sidewall of 102 mm (4.02 in). 265/35R20 sidewall is 93 mm (3.65 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 265/35R20 a safe plus-size upgrade from 255/40R19?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 1%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.