245/35R21 vs 295/30R21

295/30R21 is 0.22 in (5.5 mm) taller than 245/35R21, a +0.78% diameter difference. With the speedometer set for 245/35R21, an indicated 60 mph is 60.5 mph on 295/30R21.

Is this a safe swap?

Diameter difference +0.78%: under 1%

By overall diameter alone, 295/30R21 is a near match for 245/35R21; the speedometer changes by less than 1%. 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.

245/35R21 vs 295/30R21 differences
Measurement	245/35R21	295/30R21	Difference	% diff
Overall diameter	27.75 in (704.9 mm)	27.97 in (710.4 mm)	+0.22 in (+5.5 mm)	+0.78%
Sidewall height	3.38 in (85.8 mm)	3.48 in (88.5 mm)	+0.11 in (+2.8 mm)	+3.21%
Section width	9.65 in (245.0 mm)	11.61 in (295.0 mm)	+1.97 in (+50.0 mm)	+20.41%
Circumference	87.19 in (2,214.5 mm)	87.87 in (2,231.8 mm)	+0.68 in (+17.3 mm)	+0.78%
Revolutions per mile	727	721	−6	−0.77%

True speed with the speedometer calibrated for 245/35R21
Indicated	Actual on 245/35R21	Actual on 295/30R21	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 295/30R21 raises the vehicle by 0.11 in (2.8 mm) at the axle (half the +5.5 mm diameter difference).

295/30R21 is 0.22 in taller than 245/35R21 and 50 mm wider, a 0.78% difference in overall diameter.

With the speedometer calibrated for 245/35R21, an indicated 60 mph is actually 60.5 mph on 295/30R21, and revolutions per mile change from 727 to 721.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 245/35R21

Other comparisons with 295/30R21

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