TireSizesFinder

225/65R16 vs 235/50R18

235/50R18 is 0.26 in (6.7 mm) shorter than 225/65R16, a −0.96% diameter difference. With the speedometer set for 225/65R16, an indicated 60 mph is 59.4 mph on 235/50R18.

Is this a safe swap?

Diameter difference −0.96%: under 1%

By overall diameter alone, 235/50R18 is a near match for 225/65R16; 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: 225/65R16 (27.52 in) vs 235/50R18 (27.25 in)225/65R1627.52 in × 8.86 in235/50R1827.25 in × 9.25 in
Side profile and tread width, drawn to the same scale.
225/65R16 vs 235/50R18 differences
Measurement225/65R16235/50R18Difference% diff
Overall diameter27.52 in (698.9 mm)27.25 in (692.2 mm)−0.26 in (−6.7 mm)−0.96%
Sidewall height5.76 in (146.3 mm)4.63 in (117.5 mm)−1.13 in (−28.7 mm)−19.66%
Section width8.86 in (225.0 mm)9.25 in (235.0 mm)+0.39 in (+10.0 mm)+4.44%
Circumference86.44 in (2,195.7 mm)85.61 in (2,174.6 mm)−0.83 in (−21.0 mm)−0.96%
Revolutions per mile733740+7+0.97%
True speed with the speedometer calibrated for 225/65R16
IndicatedActual on 225/65R16Actual on 235/50R18Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.4 mph−0.6 mph
75 mph75.0 mph74.3 mph−0.7 mph

Ride-height change: 235/50R18 lowers the vehicle by 0.13 in (3.3 mm) at the axle (half the −6.7 mm diameter difference).

235/50R18 is 0.26 in shorter than 225/65R16 and 10 mm wider, a 0.96% difference in overall diameter.

With the speedometer calibrated for 225/65R16, an indicated 60 mph is actually 59.4 mph on 235/50R18, and revolutions per mile change from 733 to 740.

235/50R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 225/65R16.

Size pages

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