TireSizesFinder

235/70R17 vs 235/65R18

235/65R18 is 0.07 in (1.9 mm) taller than 235/70R17, a +0.25% diameter difference. With the speedometer set for 235/70R17, an indicated 60 mph is 60.1 mph on 235/65R18.

Is this a safe swap?

Diameter difference +0.25%: under 1%

By overall diameter alone, 235/65R18 is a near match for 235/70R17; 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: 235/70R17 (29.95 in) vs 235/65R18 (30.03 in)235/70R1729.95 in × 9.25 in235/65R1830.03 in × 9.25 in
Side profile and tread width, drawn to the same scale.
235/70R17 vs 235/65R18 differences
Measurement235/70R17235/65R18Difference% diff
Overall diameter29.95 in (760.8 mm)30.03 in (762.7 mm)+0.07 in (+1.9 mm)+0.25%
Sidewall height6.48 in (164.5 mm)6.01 in (152.8 mm)−0.46 in (−11.7 mm)−7.14%
Section width9.25 in (235.0 mm)9.25 in (235.0 mm)0.00 in (0.0 mm)0.00%
Circumference94.10 in (2,390.1 mm)94.33 in (2,396.1 mm)+0.24 in (+6.0 mm)+0.25%
Revolutions per mile673672−2−0.25%
True speed with the speedometer calibrated for 235/70R17
IndicatedActual on 235/70R17Actual on 235/65R18Difference
30 mph30.0 mph30.1 mph+0.1 mph
60 mph60.0 mph60.1 mph+0.1 mph
75 mph75.0 mph75.2 mph+0.2 mph

Ride-height change: 235/65R18 raises the vehicle by 0.04 in (1.0 mm) at the axle (half the +1.9 mm diameter difference).

235/65R18 is 0.07 in taller than 235/70R17 and the same width, a 0.25% difference in overall diameter.

With the speedometer calibrated for 235/70R17, an indicated 60 mph is actually 60.1 mph on 235/65R18, and revolutions per mile change from 673 to 672.

235/65R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 235/70R17.

Size pages

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