TireSizesFinder

275/60R17 vs 255/60R18

255/60R18 is 0.06 in (1.4 mm) taller than 275/60R17, a +0.18% diameter difference. With the speedometer set for 275/60R17, an indicated 60 mph is 60.1 mph on 255/60R18.

Is this a safe swap?

Diameter difference +0.18%: under 1%

By overall diameter alone, 255/60R18 is a near match for 275/60R17; 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: 275/60R17 (29.99 in) vs 255/60R18 (30.05 in)275/60R1729.99 in × 10.83 in255/60R1830.05 in × 10.04 in
Side profile and tread width, drawn to the same scale.
275/60R17 vs 255/60R18 differences
Measurement275/60R17255/60R18Difference% diff
Overall diameter29.99 in (761.8 mm)30.05 in (763.2 mm)+0.06 in (+1.4 mm)+0.18%
Sidewall height6.50 in (165.0 mm)6.02 in (153.0 mm)−0.47 in (−12.0 mm)−7.27%
Section width10.83 in (275.0 mm)10.04 in (255.0 mm)−0.79 in (−20.0 mm)−7.27%
Circumference94.22 in (2,393.3 mm)94.40 in (2,397.7 mm)+0.17 in (+4.4 mm)+0.18%
Revolutions per mile672671−1−0.18%
True speed with the speedometer calibrated for 275/60R17
IndicatedActual on 275/60R17Actual on 255/60R18Difference
30 mph30.0 mph30.1 mph+0.1 mph
60 mph60.0 mph60.1 mph+0.1 mph
75 mph75.0 mph75.1 mph+0.1 mph

Ride-height change: 255/60R18 raises the vehicle by 0.03 in (0.7 mm) at the axle (half the +1.4 mm diameter difference).

255/60R18 is 0.06 in taller than 275/60R17 and 20 mm narrower, a 0.18% difference in overall diameter.

With the speedometer calibrated for 275/60R17, an indicated 60 mph is actually 60.1 mph on 255/60R18, and revolutions per mile change from 672 to 671.

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

Size pages

Other comparisons with 275/60R17

Other comparisons with 255/60R18

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