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

255/35R19 has an overall diameter of 26.03 inches (661 mm). 255/40R19 is 27.03 inches (687 mm). That's a 1 inch (26 mm) difference — 255/40R19 is taller.

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

Swapping 255/35R19 for 255/40R19 produces a speedometer error of about 3.9%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 62.3 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

255/35R19 turns 775 revs per mile. 255/40R19 turns 746 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

255/35R19 has a sidewall of 89 mm (3.51 in). 255/40R19 sidewall is 102 mm (4.02 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

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

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 3.9%. This swap is outside the typical ±3% safe range and may require speedometer recalibration or affect ABS / traction control behaviour.

Tire size comparison

255/35R19 vs 255/40R19

Overall diameter, sidewall, revs per mile, and speedometer error — 255/40R19 is the taller tire, with a 3.9% speedo delta when swapping.

255/35R19

26.03in

661 mm overall diameter

255/40R19

27.03in

687 mm overall diameter

Diameter Δ

1 in

Speedo error

3.9%

255/35R19 revs/mi

775

255/40R19 revs/mi

746

Outside the typical ±3% safe plus-size band — you may want speedometer recalibration, and this change can affect ABS or traction control behaviour.

Full spec

Side by side

Metric	255/35R19	255/40R19
Section width	255 mm	255 mm
Aspect ratio	35	40
Wheel diameter	19″	19″
Sidewall height	89 mm	102 mm
Overall diameter	26.03 in (661 mm)	27.03 in (687 mm)
Circumference	81.77 in	84.92 in
Revolutions / mile	775	746

Other comparisons for these sizes

235/45R17 vs 255/35R19 245/40R18 vs 255/35R19 245/45R18 vs 255/40R19 255/40R18 vs 255/35R19 255/45R18 vs 255/40R19 235/35R19 vs 255/35R19 245/35R19 vs 255/35R19 245/40R19 vs 255/40R19 245/40R19 vs 255/35R19 245/45R19 vs 255/40R19

FAQ

Frequently asked

What is the diameter difference between 255/35R19 and 255/40R19?: 255/35R19 has an overall diameter of 26.03 inches (661 mm). 255/40R19 is 27.03 inches (687 mm). That's a 1 inch (26 mm) difference — 255/40R19 is taller.
Will 255/40R19 cause speedometer error on a car fitted with 255/35R19?: Swapping 255/35R19 for 255/40R19 produces a speedometer error of about 3.9%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 62.3 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 255/35R19 turns 775 revs per mile. 255/40R19 turns 746 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 255/35R19 has a sidewall of 89 mm (3.51 in). 255/40R19 sidewall is 102 mm (4.02 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 255/40R19 a safe plus-size upgrade from 255/35R19?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 3.9%. This swap is outside the typical ±3% safe range and may require speedometer recalibration or affect ABS / traction control behaviour.