TireSizesFinder

245/70R17 vs 245/65R18

245/65R18 is 0.04 in (0.9 mm) taller than 245/70R17, a +0.12% diameter difference. With the speedometer set for 245/70R17, an indicated 60 mph is 60.1 mph on 245/65R18.

Is this a safe swap?

Diameter difference +0.12%: under 1%

By overall diameter alone, 245/65R18 is a near match for 245/70R17; 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: 245/70R17 (30.50 in) vs 245/65R18 (30.54 in)245/70R1730.50 in × 9.65 in245/65R1830.54 in × 9.65 in
Side profile and tread width, drawn to the same scale.
245/70R17 vs 245/65R18 differences
Measurement245/70R17245/65R18Difference% diff
Overall diameter30.50 in (774.8 mm)30.54 in (775.7 mm)+0.04 in (+0.9 mm)+0.12%
Sidewall height6.75 in (171.5 mm)6.27 in (159.3 mm)−0.48 in (−12.2 mm)−7.14%
Section width9.65 in (245.0 mm)9.65 in (245.0 mm)0.00 in (0.0 mm)0.00%
Circumference95.83 in (2,434.1 mm)95.94 in (2,436.9 mm)+0.11 in (+2.8 mm)+0.12%
Revolutions per mile661660−1−0.12%
True speed with the speedometer calibrated for 245/70R17
IndicatedActual on 245/70R17Actual on 245/65R18Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph60.1 mph+0.1 mph
75 mph75.0 mph75.1 mph+0.1 mph

Ride-height change: 245/65R18 raises the vehicle by 0.02 in (0.5 mm) at the axle (half the +0.9 mm diameter difference).

245/65R18 is 0.04 in taller than 245/70R17 and the same width, a 0.12% difference in overall diameter.

With the speedometer calibrated for 245/70R17, an indicated 60 mph is actually 60.1 mph on 245/65R18, and revolutions per mile change from 661 to 660.

245/65R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 245/70R17.

Size pages

Other comparisons with 245/70R17

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