TireSizesFinder

275/30R21 vs 245/35R21

245/35R21 is 0.26 in (6.5 mm) taller than 275/30R21, a +0.93% diameter difference. With the speedometer set for 275/30R21, an indicated 60 mph is 60.6 mph on 245/35R21.

Is this a safe swap?

Diameter difference +0.93%: under 1%

By overall diameter alone, 245/35R21 is a near match for 275/30R21; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 275/30R21 (27.50 in) vs 245/35R21 (27.75 in)275/30R2127.50 in × 10.83 in245/35R2127.75 in × 9.65 in
Side profile and tread width, drawn to the same scale.
275/30R21 vs 245/35R21 differences
Measurement275/30R21245/35R21Difference% diff
Overall diameter27.50 in (698.4 mm)27.75 in (704.9 mm)+0.26 in (+6.5 mm)+0.93%
Sidewall height3.25 in (82.5 mm)3.38 in (85.8 mm)+0.13 in (+3.3 mm)+3.94%
Section width10.83 in (275.0 mm)9.65 in (245.0 mm)−1.18 in (−30.0 mm)−10.91%
Circumference86.38 in (2,194.1 mm)87.19 in (2,214.5 mm)+0.80 in (+20.4 mm)+0.93%
Revolutions per mile733727−7−0.92%
True speed with the speedometer calibrated for 275/30R21
IndicatedActual on 275/30R21Actual on 245/35R21Difference
30 mph30.0 mph30.3 mph+0.3 mph
60 mph60.0 mph60.6 mph+0.6 mph
75 mph75.0 mph75.7 mph+0.7 mph

Ride-height change: 245/35R21 raises the vehicle by 0.13 in (3.3 mm) at the axle (half the +6.5 mm diameter difference).

245/35R21 is 0.26 in taller than 275/30R21 and 30 mm narrower, a 0.93% difference in overall diameter.

With the speedometer calibrated for 275/30R21, an indicated 60 mph is actually 60.6 mph on 245/35R21, and revolutions per mile change from 733 to 727.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 275/30R21

Other comparisons with 245/35R21

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.