TireSizesFinder

255/50R19 vs 265/40R21

265/40R21 is 0.31 in (7.8 mm) taller than 255/50R19, a +1.06% diameter difference. With the speedometer set for 255/50R19, an indicated 60 mph is 60.6 mph on 265/40R21.

Is this a safe swap?

Diameter difference +1.06%: within the ±3% guideline

By overall diameter alone, 265/40R21 falls inside the ±3% range commonly used as a guideline when replacing 255/50R19. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 255/50R19 (29.04 in) vs 265/40R21 (29.35 in)255/50R1929.04 in × 10.04 in265/40R2129.35 in × 10.43 in
Side profile and tread width, drawn to the same scale.
255/50R19 vs 265/40R21 differences
Measurement255/50R19265/40R21Difference% diff
Overall diameter29.04 in (737.6 mm)29.35 in (745.4 mm)+0.31 in (+7.8 mm)+1.06%
Sidewall height5.02 in (127.5 mm)4.17 in (106.0 mm)−0.85 in (−21.5 mm)−16.86%
Section width10.04 in (255.0 mm)10.43 in (265.0 mm)+0.39 in (+10.0 mm)+3.92%
Circumference91.23 in (2,317.2 mm)92.19 in (2,341.7 mm)+0.96 in (+24.5 mm)+1.06%
Revolutions per mile695687−7−1.05%
True speed with the speedometer calibrated for 255/50R19
IndicatedActual on 255/50R19Actual on 265/40R21Difference
30 mph30.0 mph30.3 mph+0.3 mph
60 mph60.0 mph60.6 mph+0.6 mph
75 mph75.0 mph75.8 mph+0.8 mph

Ride-height change: 265/40R21 raises the vehicle by 0.15 in (3.9 mm) at the axle (half the +7.8 mm diameter difference).

265/40R21 is 0.31 in taller than 255/50R19 and 10 mm wider, a 1.06% difference in overall diameter.

With the speedometer calibrated for 255/50R19, an indicated 60 mph is actually 60.6 mph on 265/40R21, and revolutions per mile change from 695 to 687.

265/40R21 mounts on a 21-inch wheel, a plus-2 fitment from the 19-inch wheel of 255/50R19.

Size pages

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