What is the diameter difference between 235/45R17 and 255/35R19?

235/45R17 has an overall diameter of 25.33 inches (643 mm). 255/35R19 is 26.03 inches (661 mm). That's a 0.7 inch (18 mm) difference — 255/35R19 is taller.

Will 255/35R19 cause speedometer error on a car fitted with 235/45R17?

Swapping 235/45R17 for 255/35R19 produces a speedometer error of about 2.8%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 61.7 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

235/45R17 turns 796 revs per mile. 255/35R19 turns 775 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

235/45R17 has a sidewall of 106 mm (4.16 in). 255/35R19 sidewall is 89 mm (3.51 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 255/35R19 a safe plus-size upgrade from 235/45R17?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 2.8%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.

Tire size comparison

235/45R17 vs 255/35R19

Overall diameter, sidewall, revs per mile, and speedometer error — 255/35R19 is the taller tire, with a 2.8% speedo delta when swapping.

235/45R17

25.33in

643 mm overall diameter

255/35R19

26.03in

661 mm overall diameter

Diameter Δ

0.7 in

Speedo error

2.8%

235/45R17 revs/mi

796

255/35R19 revs/mi

775

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	235/45R17	255/35R19
Section width	235 mm	255 mm
Aspect ratio	45	35
Wheel diameter	17″	19″
Sidewall height	106 mm	89 mm
Overall diameter	25.33 in (643 mm)	26.03 in (661 mm)
Circumference	79.57 in	81.77 in
Revolutions / mile	796	775

Other comparisons for these sizes

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

FAQ

Frequently asked

What is the diameter difference between 235/45R17 and 255/35R19?: 235/45R17 has an overall diameter of 25.33 inches (643 mm). 255/35R19 is 26.03 inches (661 mm). That's a 0.7 inch (18 mm) difference — 255/35R19 is taller.
Will 255/35R19 cause speedometer error on a car fitted with 235/45R17?: Swapping 235/45R17 for 255/35R19 produces a speedometer error of about 2.8%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 61.7 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 235/45R17 turns 796 revs per mile. 255/35R19 turns 775 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 235/45R17 has a sidewall of 106 mm (4.16 in). 255/35R19 sidewall is 89 mm (3.51 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 255/35R19 a safe plus-size upgrade from 235/45R17?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 2.8%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.