TireSizesFinder

245/45R19 vs 275/30R21

275/30R21 is 0.19 in (4.7 mm) shorter than 245/45R19, a −0.67% diameter difference. With the speedometer set for 245/45R19, an indicated 60 mph is 59.6 mph on 275/30R21.

Is this a safe swap?

Diameter difference −0.67%: under 1%

By overall diameter alone, 275/30R21 is a near match for 245/45R19; 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: 245/45R19 (27.68 in) vs 275/30R21 (27.50 in)245/45R1927.68 in × 9.65 in275/30R2127.50 in × 10.83 in
Side profile and tread width, drawn to the same scale.
245/45R19 vs 275/30R21 differences
Measurement245/45R19275/30R21Difference% diff
Overall diameter27.68 in (703.1 mm)27.50 in (698.4 mm)−0.19 in (−4.7 mm)−0.67%
Sidewall height4.34 in (110.3 mm)3.25 in (82.5 mm)−1.09 in (−27.7 mm)−25.17%
Section width9.65 in (245.0 mm)10.83 in (275.0 mm)+1.18 in (+30.0 mm)+12.24%
Circumference86.96 in (2,208.9 mm)86.38 in (2,194.1 mm)−0.58 in (−14.8 mm)−0.67%
Revolutions per mile729733+5+0.67%
True speed with the speedometer calibrated for 245/45R19
IndicatedActual on 245/45R19Actual on 275/30R21Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.6 mph−0.4 mph
75 mph75.0 mph74.5 mph−0.5 mph

Ride-height change: 275/30R21 lowers the vehicle by 0.09 in (2.3 mm) at the axle (half the −4.7 mm diameter difference).

275/30R21 is 0.19 in shorter than 245/45R19 and 30 mm wider, a 0.67% difference in overall diameter.

With the speedometer calibrated for 245/45R19, an indicated 60 mph is actually 59.6 mph on 275/30R21, and revolutions per mile change from 729 to 733.

275/30R21 mounts on a 21-inch wheel, a plus-2 fitment from the 19-inch wheel of 245/45R19.

Size pages

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