What is the diameter difference between 295/30R20 and 295/35R20?

295/30R20 has an overall diameter of 26.97 inches (685 mm). 295/35R20 is 28.13 inches (715 mm). That's a 1.16 inch (30 mm) difference — 295/35R20 is taller.

Will 295/35R20 cause speedometer error on a car fitted with 295/30R20?

Swapping 295/30R20 for 295/35R20 produces a speedometer error of about 4.3%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 62.6 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

295/30R20 turns 748 revs per mile. 295/35R20 turns 717 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

295/30R20 has a sidewall of 89 mm (3.48 in). 295/35R20 sidewall is 103 mm (4.06 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 295/35R20 a safe plus-size upgrade from 295/30R20?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 4.3%. This swap is outside the typical ±3% safe range and may require speedometer recalibration or affect ABS / traction control behaviour.

Tire size comparison

295/30R20 vs 295/35R20

Overall diameter, sidewall, revs per mile, and speedometer error — 295/35R20 is the taller tire, with a 4.3% speedo delta when swapping.

295/30R20

26.97in

685 mm overall diameter

295/35R20

28.13in

715 mm overall diameter

Diameter Δ

1.16 in

Speedo error

4.3%

295/30R20 revs/mi

748

295/35R20 revs/mi

717

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	295/30R20	295/35R20
Section width	295 mm	295 mm
Aspect ratio	30	35
Wheel diameter	20″	20″
Sidewall height	89 mm	103 mm
Overall diameter	26.97 in (685 mm)	28.13 in (715 mm)
Circumference	84.72 in	88.37 in
Revolutions / mile	748	717

Other comparisons for these sizes

275/40R18 vs 295/30R20 275/30R20 vs 295/30R20 275/35R20 vs 295/35R20 285/30R20 vs 295/30R20 285/35R20 vs 295/35R20 285/35R20 vs 295/30R20 295/30R20 vs 305/30R20 295/35R20 vs 305/30R21 295/35R20 vs 295/30R21 295/35R20 vs 305/35R20

FAQ

Frequently asked

What is the diameter difference between 295/30R20 and 295/35R20?: 295/30R20 has an overall diameter of 26.97 inches (685 mm). 295/35R20 is 28.13 inches (715 mm). That's a 1.16 inch (30 mm) difference — 295/35R20 is taller.
Will 295/35R20 cause speedometer error on a car fitted with 295/30R20?: Swapping 295/30R20 for 295/35R20 produces a speedometer error of about 4.3%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 62.6 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 295/30R20 turns 748 revs per mile. 295/35R20 turns 717 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 295/30R20 has a sidewall of 89 mm (3.48 in). 295/35R20 sidewall is 103 mm (4.06 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 295/35R20 a safe plus-size upgrade from 295/30R20?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 4.3%. This swap is outside the typical ±3% safe range and may require speedometer recalibration or affect ABS / traction control behaviour.