What is the diameter difference between 245/40R19 and 245/35R20?

245/40R19 has an overall diameter of 26.72 inches (679 mm). 245/35R20 is 26.75 inches (680 mm). That's a 0.04 inch (1 mm) difference — 245/35R20 is taller.

Will 245/35R20 cause speedometer error on a car fitted with 245/40R19?

Swapping 245/40R19 for 245/35R20 produces a speedometer error of about 0.1%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 60.1 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

245/40R19 turns 755 revs per mile. 245/35R20 turns 754 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

245/40R19 has a sidewall of 98 mm (3.86 in). 245/35R20 sidewall is 86 mm (3.38 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 245/35R20 a safe plus-size upgrade from 245/40R19?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 0.1%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.

Tire size comparison

245/40R19 vs 245/35R20

Overall diameter, sidewall, revs per mile, and speedometer error — 245/35R20 is the taller tire, with a 0.1% speedo delta when swapping.

245/40R19

26.72in

679 mm overall diameter

245/35R20

26.75in

680 mm overall diameter

Diameter Δ

0.04 in

Speedo error

0.1%

245/40R19 revs/mi

755

245/35R20 revs/mi

754

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	245/40R19	245/35R20
Section width	245 mm	245 mm
Aspect ratio	40	35
Wheel diameter	19″	20″
Sidewall height	98 mm	86 mm
Overall diameter	26.72 in (679 mm)	26.75 in (680 mm)
Circumference	83.93 in	84.04 in
Revolutions / mile	755	754

Other comparisons for these sizes

225/50R17 vs 245/40R19 225/45R18 vs 245/35R20 235/45R18 vs 245/40R19 245/45R18 vs 245/40R19 225/40R19 vs 245/40R19 245/35R19 vs 245/40R19 245/40R19 vs 255/35R20 245/40R19 vs 255/40R19 245/40R19 vs 245/45R19 245/40R19 vs 255/35R19

FAQ

Frequently asked

What is the diameter difference between 245/40R19 and 245/35R20?: 245/40R19 has an overall diameter of 26.72 inches (679 mm). 245/35R20 is 26.75 inches (680 mm). That's a 0.04 inch (1 mm) difference — 245/35R20 is taller.
Will 245/35R20 cause speedometer error on a car fitted with 245/40R19?: Swapping 245/40R19 for 245/35R20 produces a speedometer error of about 0.1%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 60.1 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 245/40R19 turns 755 revs per mile. 245/35R20 turns 754 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 245/40R19 has a sidewall of 98 mm (3.86 in). 245/35R20 sidewall is 86 mm (3.38 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 245/35R20 a safe plus-size upgrade from 245/40R19?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 0.1%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.