What is the diameter difference between 265/30R20 and 265/35R20?

265/30R20 has an overall diameter of 26.26 inches (667 mm). 265/35R20 is 27.3 inches (694 mm). That's a 1.04 inch (27 mm) difference — 265/35R20 is taller.

Will 265/35R20 cause speedometer error on a car fitted with 265/30R20?

Swapping 265/30R20 for 265/35R20 produces a speedometer error of about 4%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 62.4 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

265/30R20 turns 768 revs per mile. 265/35R20 turns 739 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

265/30R20 has a sidewall of 80 mm (3.13 in). 265/35R20 sidewall is 93 mm (3.65 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 265/35R20 a safe plus-size upgrade from 265/30R20?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 4%. This swap is outside the typical ±3% safe range and may require speedometer recalibration or affect ABS / traction control behaviour.

Tire size comparison

265/30R20 vs 265/35R20

Overall diameter, sidewall, revs per mile, and speedometer error — 265/35R20 is the taller tire, with a 4% speedo delta when swapping.

265/30R20

26.26in

667 mm overall diameter

265/35R20

27.3in

694 mm overall diameter

Diameter Δ

1.04 in

Speedo error

265/30R20 revs/mi

768

265/35R20 revs/mi

739

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	265/30R20	265/35R20
Section width	265 mm	265 mm
Aspect ratio	30	35
Wheel diameter	20″	20″
Sidewall height	80 mm	93 mm
Overall diameter	26.26 in (667 mm)	27.3 in (694 mm)
Circumference	82.5 in	85.78 in
Revolutions / mile	768	739

Other comparisons for these sizes

245/40R18 vs 265/30R20 245/45R18 vs 265/35R20 255/35R19 vs 265/30R20 255/40R19 vs 265/35R20 265/35R19 vs 265/30R20 245/35R20 vs 265/35R20 255/30R20 vs 265/30R20 255/35R20 vs 265/35R20 255/35R20 vs 265/30R20 265/30R20 vs 275/30R20

FAQ

Frequently asked

What is the diameter difference between 265/30R20 and 265/35R20?: 265/30R20 has an overall diameter of 26.26 inches (667 mm). 265/35R20 is 27.3 inches (694 mm). That's a 1.04 inch (27 mm) difference — 265/35R20 is taller.
Will 265/35R20 cause speedometer error on a car fitted with 265/30R20?: Swapping 265/30R20 for 265/35R20 produces a speedometer error of about 4%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 62.4 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 265/30R20 turns 768 revs per mile. 265/35R20 turns 739 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 265/30R20 has a sidewall of 80 mm (3.13 in). 265/35R20 sidewall is 93 mm (3.65 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 265/35R20 a safe plus-size upgrade from 265/30R20?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 4%. This swap is outside the typical ±3% safe range and may require speedometer recalibration or affect ABS / traction control behaviour.