275/30R21 vs 295/30R21

295/30R21 is 0.47 in (12.0 mm) taller than 275/30R21, a +1.72% diameter difference. With the speedometer set for 275/30R21, an indicated 60 mph is 61.0 mph on 295/30R21.

Is this a safe swap?

Diameter difference +1.72%: within the ±3% guideline

By overall diameter alone, 295/30R21 falls inside the ±3% range commonly used as a guideline when replacing 275/30R21. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

275/30R21 vs 295/30R21 differences
Measurement	275/30R21	295/30R21	Difference	% diff
Overall diameter	27.50 in (698.4 mm)	27.97 in (710.4 mm)	+0.47 in (+12.0 mm)	+1.72%
Sidewall height	3.25 in (82.5 mm)	3.48 in (88.5 mm)	+0.24 in (+6.0 mm)	+7.27%
Section width	10.83 in (275.0 mm)	11.61 in (295.0 mm)	+0.79 in (+20.0 mm)	+7.27%
Circumference	86.38 in (2,194.1 mm)	87.87 in (2,231.8 mm)	+1.48 in (+37.7 mm)	+1.72%
Revolutions per mile	733	721	−12	−1.69%

True speed with the speedometer calibrated for 275/30R21
Indicated	Actual on 275/30R21	Actual on 295/30R21	Difference
30 mph	30.0 mph	30.5 mph	+0.5 mph
60 mph	60.0 mph	61.0 mph	+1.0 mph
75 mph	75.0 mph	76.3 mph	+1.3 mph

Ride-height change: 295/30R21 raises the vehicle by 0.24 in (6.0 mm) at the axle (half the +12.0 mm diameter difference).

295/30R21 is 0.47 in taller than 275/30R21 and 20 mm wider, a 1.72% difference in overall diameter.

With the speedometer calibrated for 275/30R21, an indicated 60 mph is actually 61.0 mph on 295/30R21, and revolutions per mile change from 733 to 721.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 275/30R21

Other comparisons with 295/30R21

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.