What is the diameter difference between 275/40R18 and 275/35R19?

275/40R18 has an overall diameter of 26.66 inches (677 mm). 275/35R19 is 26.58 inches (675 mm). That's a 0.08 inch (2 mm) difference — 275/35R19 is shorter.

Will 275/35R19 cause speedometer error on a car fitted with 275/40R18?

Swapping 275/40R18 for 275/35R19 produces a speedometer error of about 0.3%. Your speedometer will read higher than your actual speed — a 60 mph indicated reading is really 59.8 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

275/40R18 turns 756 revs per mile. 275/35R19 turns 759 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

275/40R18 has a sidewall of 110 mm (4.33 in). 275/35R19 sidewall is 96 mm (3.79 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 275/35R19 a safe plus-size upgrade from 275/40R18?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 0.3%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.

Tire size comparison

275/40R18 vs 275/35R19

Overall diameter, sidewall, revs per mile, and speedometer error — 275/40R18 is the taller tire, with a 0.3% speedo delta when swapping.

275/40R18

26.66in

677 mm overall diameter

275/35R19

26.58in

675 mm overall diameter

Diameter Δ

0.08 in

Speedo error

0.3%

275/40R18 revs/mi

756

275/35R19 revs/mi

759

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	275/40R18	275/35R19
Section width	275 mm	275 mm
Aspect ratio	40	35
Wheel diameter	18″	19″
Sidewall height	110 mm	96 mm
Overall diameter	26.66 in (677 mm)	26.58 in (675 mm)
Circumference	83.76 in	83.5 in
Revolutions / mile	756	759

Other comparisons for these sizes

255/40R18 vs 275/40R18 275/35R18 vs 275/40R18 275/40R18 vs 295/30R20 255/35R19 vs 275/35R19 265/35R19 vs 275/35R19 275/30R19 vs 275/35R19 275/35R19 vs 285/30R20 275/35R19 vs 275/30R20 275/35R19 vs 285/30R19

FAQ

Frequently asked

What is the diameter difference between 275/40R18 and 275/35R19?: 275/40R18 has an overall diameter of 26.66 inches (677 mm). 275/35R19 is 26.58 inches (675 mm). That's a 0.08 inch (2 mm) difference — 275/35R19 is shorter.
Will 275/35R19 cause speedometer error on a car fitted with 275/40R18?: Swapping 275/40R18 for 275/35R19 produces a speedometer error of about 0.3%. Your speedometer will read higher than your actual speed — a 60 mph indicated reading is really 59.8 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 275/40R18 turns 756 revs per mile. 275/35R19 turns 759 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 275/40R18 has a sidewall of 110 mm (4.33 in). 275/35R19 sidewall is 96 mm (3.79 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 275/35R19 a safe plus-size upgrade from 275/40R18?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 0.3%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.