TireSizesFinder

205/75R16 vs 255/50R18

255/50R18 is 0.07 in (1.7 mm) shorter than 205/75R16, a −0.24% diameter difference. With the speedometer set for 205/75R16, an indicated 60 mph is 59.9 mph on 255/50R18.

Is this a safe swap?

Diameter difference −0.24%: under 1%

By overall diameter alone, 255/50R18 is a near match for 205/75R16; 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: 205/75R16 (28.11 in) vs 255/50R18 (28.04 in)205/75R1628.11 in × 8.07 in255/50R1828.04 in × 10.04 in
Side profile and tread width, drawn to the same scale.
205/75R16 vs 255/50R18 differences
Measurement205/75R16255/50R18Difference% diff
Overall diameter28.11 in (713.9 mm)28.04 in (712.2 mm)−0.07 in (−1.7 mm)−0.24%
Sidewall height6.05 in (153.8 mm)5.02 in (127.5 mm)−1.03 in (−26.2 mm)−17.07%
Section width8.07 in (205.0 mm)10.04 in (255.0 mm)+1.97 in (+50.0 mm)+24.39%
Circumference88.30 in (2,242.8 mm)88.09 in (2,237.4 mm)−0.21 in (−5.3 mm)−0.24%
Revolutions per mile718719+2+0.24%
True speed with the speedometer calibrated for 205/75R16
IndicatedActual on 205/75R16Actual on 255/50R18Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.9 mph−0.1 mph
75 mph75.0 mph74.8 mph−0.2 mph

Ride-height change: 255/50R18 lowers the vehicle by 0.03 in (0.8 mm) at the axle (half the −1.7 mm diameter difference).

255/50R18 is 0.07 in shorter than 205/75R16 and 50 mm wider, a 0.24% difference in overall diameter.

With the speedometer calibrated for 205/75R16, an indicated 60 mph is actually 59.9 mph on 255/50R18, and revolutions per mile change from 718 to 719.

255/50R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 205/75R16.

Size pages

Other comparisons with 205/75R16

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