What is the diameter difference between 275/60R20 and 285/60R20?

275/60R20 has an overall diameter of 32.99 inches (838 mm). 285/60R20 is 33.46 inches (850 mm). That's a 0.47 inch (12 mm) difference — 285/60R20 is taller.

Will 285/60R20 cause speedometer error on a car fitted with 275/60R20?

Swapping 275/60R20 for 285/60R20 produces a speedometer error of about 1.4%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 60.9 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

275/60R20 turns 611 revs per mile. 285/60R20 turns 603 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

275/60R20 has a sidewall of 165 mm (6.5 in). 285/60R20 sidewall is 171 mm (6.73 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 285/60R20 a safe plus-size upgrade from 275/60R20?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 1.4%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.

Tire size comparison

275/60R20 vs 285/60R20

Overall diameter, sidewall, revs per mile, and speedometer error — 285/60R20 is the taller tire, with a 1.4% speedo delta when swapping.

275/60R20

32.99in

838 mm overall diameter

285/60R20

33.46in

850 mm overall diameter

Diameter Δ

0.47 in

Speedo error

1.4%

275/60R20 revs/mi

611

285/60R20 revs/mi

603

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	275/60R20	285/60R20
Section width	275 mm	285 mm
Aspect ratio	60	60
Wheel diameter	20″	20″
Sidewall height	165 mm	171 mm
Overall diameter	32.99 in (838 mm)	33.46 in (850 mm)
Circumference	103.65 in	105.13 in
Revolutions / mile	611	603

FAQ

Frequently asked

What is the diameter difference between 275/60R20 and 285/60R20?: 275/60R20 has an overall diameter of 32.99 inches (838 mm). 285/60R20 is 33.46 inches (850 mm). That's a 0.47 inch (12 mm) difference — 285/60R20 is taller.
Will 285/60R20 cause speedometer error on a car fitted with 275/60R20?: Swapping 275/60R20 for 285/60R20 produces a speedometer error of about 1.4%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 60.9 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 275/60R20 turns 611 revs per mile. 285/60R20 turns 603 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 275/60R20 has a sidewall of 165 mm (6.5 in). 285/60R20 sidewall is 171 mm (6.73 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 285/60R20 a safe plus-size upgrade from 275/60R20?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 1.4%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.