TireSizesFinder

255/70R16 vs 235/65R18

235/65R18 is 0.03 in (0.7 mm) shorter than 255/70R16, a −0.09% diameter difference. With the speedometer set for 255/70R16, an indicated 60 mph is 59.9 mph on 235/65R18.

Is this a safe swap?

Diameter difference −0.09%: under 1%

By overall diameter alone, 235/65R18 is a near match for 255/70R16; 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: 255/70R16 (30.06 in) vs 235/65R18 (30.03 in)255/70R1630.06 in × 10.04 in235/65R1830.03 in × 9.25 in
Side profile and tread width, drawn to the same scale.
255/70R16 vs 235/65R18 differences
Measurement255/70R16235/65R18Difference% diff
Overall diameter30.06 in (763.4 mm)30.03 in (762.7 mm)−0.03 in (−0.7 mm)−0.09%
Sidewall height7.03 in (178.5 mm)6.01 in (152.8 mm)−1.01 in (−25.7 mm)−14.43%
Section width10.04 in (255.0 mm)9.25 in (235.0 mm)−0.79 in (−20.0 mm)−7.84%
Circumference94.42 in (2,398.3 mm)94.33 in (2,396.1 mm)−0.09 in (−2.2 mm)−0.09%
Revolutions per mile671672+1+0.09%
True speed with the speedometer calibrated for 255/70R16
IndicatedActual on 255/70R16Actual on 235/65R18Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph59.9 mph−0.1 mph
75 mph75.0 mph74.9 mph−0.1 mph

Ride-height change: 235/65R18 lowers the vehicle by 0.01 in (0.3 mm) at the axle (half the −0.7 mm diameter difference).

235/65R18 is 0.03 in shorter than 255/70R16 and 20 mm narrower, a 0.09% difference in overall diameter.

With the speedometer calibrated for 255/70R16, an indicated 60 mph is actually 59.9 mph on 235/65R18, and revolutions per mile change from 671 to 672.

235/65R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 255/70R16.

Size pages

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