TireSizesFinder

255/70R17 vs 275/60R18

275/60R18 is 0.06 in (1.6 mm) shorter than 255/70R17, a −0.20% diameter difference. With the speedometer set for 255/70R17, an indicated 60 mph is 59.9 mph on 275/60R18.

Is this a safe swap?

Diameter difference −0.20%: under 1%

By overall diameter alone, 275/60R18 is a near match for 255/70R17; 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: 255/70R17 (31.06 in) vs 275/60R18 (30.99 in)255/70R1731.06 in × 10.04 in275/60R1830.99 in × 10.83 in
Side profile and tread width, drawn to the same scale.
255/70R17 vs 275/60R18 differences
Measurement255/70R17275/60R18Difference% diff
Overall diameter31.06 in (788.8 mm)30.99 in (787.2 mm)−0.06 in (−1.6 mm)−0.20%
Sidewall height7.03 in (178.5 mm)6.50 in (165.0 mm)−0.53 in (−13.5 mm)−7.56%
Section width10.04 in (255.0 mm)10.83 in (275.0 mm)+0.79 in (+20.0 mm)+7.84%
Circumference97.56 in (2,478.1 mm)97.36 in (2,473.1 mm)−0.20 in (−5.0 mm)−0.20%
Revolutions per mile649651+1+0.20%
True speed with the speedometer calibrated for 255/70R17
IndicatedActual on 255/70R17Actual on 275/60R18Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.9 mph−0.1 mph
75 mph75.0 mph74.8 mph−0.2 mph

Ride-height change: 275/60R18 lowers the vehicle by 0.03 in (0.8 mm) at the axle (half the −1.6 mm diameter difference).

275/60R18 is 0.06 in shorter than 255/70R17 and 20 mm wider, a 0.20% difference in overall diameter.

With the speedometer calibrated for 255/70R17, an indicated 60 mph is actually 59.9 mph on 275/60R18, and revolutions per mile change from 649 to 651.

275/60R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 255/70R17.

Size pages

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