TireSizesFinder

255/45R20 vs 255/50R20

255/50R20 is 1.00 in (25.5 mm) taller than 255/45R20, a +3.46% diameter difference. With the speedometer set for 255/45R20, an indicated 60 mph is 62.1 mph on 255/50R20.

Is this a safe swap?

Diameter difference +3.46%: outside the ±3% guideline

By overall diameter alone, 255/50R20 falls outside the ±3% range commonly used as a guideline when replacing 255/45R20; speedometer and ride-height changes are larger. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 255/45R20 (29.04 in) vs 255/50R20 (30.04 in)255/45R2029.04 in × 10.04 in255/50R2030.04 in × 10.04 in
Side profile and tread width, drawn to the same scale.
255/45R20 vs 255/50R20 differences
Measurement255/45R20255/50R20Difference% diff
Overall diameter29.04 in (737.5 mm)30.04 in (763.0 mm)+1.00 in (+25.5 mm)+3.46%
Sidewall height4.52 in (114.8 mm)5.02 in (127.5 mm)+0.50 in (+12.8 mm)+11.11%
Section width10.04 in (255.0 mm)10.04 in (255.0 mm)0.00 in (0.0 mm)0.00%
Circumference91.22 in (2,316.9 mm)94.37 in (2,397.0 mm)+3.15 in (+80.1 mm)+3.46%
Revolutions per mile695671−23−3.34%
True speed with the speedometer calibrated for 255/45R20
IndicatedActual on 255/45R20Actual on 255/50R20Difference
30 mph30.0 mph31.0 mph+1.0 mph
60 mph60.0 mph62.1 mph+2.1 mph
75 mph75.0 mph77.6 mph+2.6 mph

Ride-height change: 255/50R20 raises the vehicle by 0.50 in (12.8 mm) at the axle (half the +25.5 mm diameter difference).

255/50R20 is 1.00 in taller than 255/45R20 and the same width, a 3.46% difference in overall diameter.

With the speedometer calibrated for 255/45R20, an indicated 60 mph is actually 62.1 mph on 255/50R20, and revolutions per mile change from 695 to 671.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 255/45R20

Other comparisons with 255/50R20

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