TireSizesFinder

285/75R17 vs 275/70R18

275/70R18 is 0.67 in (17.1 mm) shorter than 285/75R17, a −1.99% diameter difference. With the speedometer set for 285/75R17, an indicated 60 mph is 58.8 mph on 275/70R18.

Is this a safe swap?

Diameter difference −1.99%: within the ±3% guideline

By overall diameter alone, 275/70R18 falls inside the ±3% range commonly used as a guideline when replacing 285/75R17. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 285/75R17 (33.83 in) vs 275/70R18 (33.16 in)285/75R1733.83 in × 11.22 in275/70R1833.16 in × 10.83 in
Side profile and tread width, drawn to the same scale.
285/75R17 vs 275/70R18 differences
Measurement285/75R17275/70R18Difference% diff
Overall diameter33.83 in (859.3 mm)33.16 in (842.2 mm)−0.67 in (−17.1 mm)−1.99%
Sidewall height8.42 in (213.8 mm)7.58 in (192.5 mm)−0.84 in (−21.2 mm)−9.94%
Section width11.22 in (285.0 mm)10.83 in (275.0 mm)−0.39 in (−10.0 mm)−3.51%
Circumference106.28 in (2,699.6 mm)104.17 in (2,645.8 mm)−2.12 in (−53.7 mm)−1.99%
Revolutions per mile596608+12+2.03%
True speed with the speedometer calibrated for 285/75R17
IndicatedActual on 285/75R17Actual on 275/70R18Difference
30 mph30.0 mph29.4 mph−0.6 mph
60 mph60.0 mph58.8 mph−1.2 mph
75 mph75.0 mph73.5 mph−1.5 mph

Ride-height change: 275/70R18 lowers the vehicle by 0.34 in (8.5 mm) at the axle (half the −17.1 mm diameter difference).

275/70R18 is 0.67 in shorter than 285/75R17 and 10 mm narrower, a 1.99% difference in overall diameter.

With the speedometer calibrated for 285/75R17, an indicated 60 mph is actually 58.8 mph on 275/70R18, and revolutions per mile change from 596 to 608.

275/70R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 285/75R17.

Size pages

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