TireSizesFinder

275/55R20 vs 275/50R21

275/50R21 is 0.08 in (2.1 mm) shorter than 275/55R20, a −0.26% diameter difference. With the speedometer set for 275/55R20, an indicated 60 mph is 59.8 mph on 275/50R21.

Is this a safe swap?

Diameter difference −0.26%: under 1%

By overall diameter alone, 275/50R21 is a near match for 275/55R20; 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: 275/55R20 (31.91 in) vs 275/50R21 (31.83 in)275/55R2031.91 in × 10.83 in275/50R2131.83 in × 10.83 in
Side profile and tread width, drawn to the same scale.
275/55R20 vs 275/50R21 differences
Measurement275/55R20275/50R21Difference% diff
Overall diameter31.91 in (810.5 mm)31.83 in (808.4 mm)−0.08 in (−2.1 mm)−0.26%
Sidewall height5.95 in (151.3 mm)5.41 in (137.5 mm)−0.54 in (−13.7 mm)−9.09%
Section width10.83 in (275.0 mm)10.83 in (275.0 mm)0.00 in (0.0 mm)0.00%
Circumference100.25 in (2,546.3 mm)99.99 in (2,539.7 mm)−0.26 in (−6.6 mm)−0.26%
Revolutions per mile632634+2+0.26%
True speed with the speedometer calibrated for 275/55R20
IndicatedActual on 275/55R20Actual on 275/50R21Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.8 mph−0.2 mph
75 mph75.0 mph74.8 mph−0.2 mph

Ride-height change: 275/50R21 lowers the vehicle by 0.04 in (1.1 mm) at the axle (half the −2.1 mm diameter difference).

275/50R21 is 0.08 in shorter than 275/55R20 and the same width, a 0.26% difference in overall diameter.

With the speedometer calibrated for 275/55R20, an indicated 60 mph is actually 59.8 mph on 275/50R21, and revolutions per mile change from 632 to 634.

275/50R21 mounts on a 21-inch wheel, a plus-1 fitment from the 20-inch wheel of 275/55R20.

Size pages

Other comparisons with 275/55R20

Other comparisons with 275/50R21

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