What is the diameter difference between 275/35R21 and 295/35R21?

275/35R21 has an overall diameter of 28.58 inches (726 mm). 295/35R21 is 29.13 inches (740 mm). That's a 0.55 inch (14 mm) difference — 295/35R21 is taller.

Will 295/35R21 cause speedometer error on a car fitted with 275/35R21?

Swapping 275/35R21 for 295/35R21 produces a speedometer error of about 1.9%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 61.2 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

275/35R21 turns 706 revs per mile. 295/35R21 turns 692 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

275/35R21 has a sidewall of 96 mm (3.79 in). 295/35R21 sidewall is 103 mm (4.06 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 295/35R21 a safe plus-size upgrade from 275/35R21?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 1.9%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.

Tire size comparison

275/35R21 vs 295/35R21

Overall diameter, sidewall, revs per mile, and speedometer error — 295/35R21 is the taller tire, with a 1.9% speedo delta when swapping.

275/35R21

28.58in

726 mm overall diameter

295/35R21

29.13in

740 mm overall diameter

Diameter Δ

0.55 in

Speedo error

1.9%

275/35R21 revs/mi

706

295/35R21 revs/mi

692

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	275/35R21	295/35R21
Section width	275 mm	295 mm
Aspect ratio	35	35
Wheel diameter	21″	21″
Sidewall height	96 mm	103 mm
Overall diameter	28.58 in (726 mm)	29.13 in (740 mm)
Circumference	89.78 in	91.51 in
Revolutions / mile	706	692

Other comparisons for these sizes

255/35R21 vs 275/35R21 265/35R21 vs 275/35R21 275/30R21 vs 275/35R21 275/35R21 vs 285/30R22 275/35R21 vs 285/30R21 295/30R21 vs 295/35R21 295/35R21 vs 305/30R22 295/35R21 vs 295/30R22 295/35R21 vs 305/30R21

FAQ

Frequently asked

What is the diameter difference between 275/35R21 and 295/35R21?: 275/35R21 has an overall diameter of 28.58 inches (726 mm). 295/35R21 is 29.13 inches (740 mm). That's a 0.55 inch (14 mm) difference — 295/35R21 is taller.
Will 295/35R21 cause speedometer error on a car fitted with 275/35R21?: Swapping 275/35R21 for 295/35R21 produces a speedometer error of about 1.9%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 61.2 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 275/35R21 turns 706 revs per mile. 295/35R21 turns 692 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 275/35R21 has a sidewall of 96 mm (3.79 in). 295/35R21 sidewall is 103 mm (4.06 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 295/35R21 a safe plus-size upgrade from 275/35R21?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 1.9%. This swap is within the typical safe range; speedometer and ABS calibration should remain close to factory.