275/65R17 vs 265/65R18

265/65R18 is 0.49 in (12.4 mm) taller than 275/65R17, a +1.57% diameter difference. With the speedometer set for 275/65R17, an indicated 60 mph is 60.9 mph on 265/65R18.

Is this a safe swap?

Diameter difference +1.57%: within the ±3% guideline

By overall diameter alone, 265/65R18 falls inside the ±3% range commonly used as a guideline when replacing 275/65R17. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

275/65R17 vs 265/65R18 differences
Measurement	275/65R17	265/65R18	Difference	% diff
Overall diameter	31.07 in (789.3 mm)	31.56 in (801.7 mm)	+0.49 in (+12.4 mm)	+1.57%
Sidewall height	7.04 in (178.8 mm)	6.78 in (172.3 mm)	−0.26 in (−6.5 mm)	−3.64%
Section width	10.83 in (275.0 mm)	10.43 in (265.0 mm)	−0.39 in (−10.0 mm)	−3.64%
Circumference	97.62 in (2,479.7 mm)	99.16 in (2,518.6 mm)	+1.53 in (+39.0 mm)	+1.57%
Revolutions per mile	649	639	−10	−1.55%

True speed with the speedometer calibrated for 275/65R17
Indicated	Actual on 275/65R17	Actual on 265/65R18	Difference
30 mph	30.0 mph	30.5 mph	+0.5 mph
60 mph	60.0 mph	60.9 mph	+0.9 mph
75 mph	75.0 mph	76.2 mph	+1.2 mph

Ride-height change: 265/65R18 raises the vehicle by 0.24 in (6.2 mm) at the axle (half the +12.4 mm diameter difference).

265/65R18 is 0.49 in taller than 275/65R17 and 10 mm narrower, a 1.57% difference in overall diameter.

With the speedometer calibrated for 275/65R17, an indicated 60 mph is actually 60.9 mph on 265/65R18, and revolutions per mile change from 649 to 639.

265/65R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 275/65R17.

Size pages

Other comparisons with 275/65R17

Other comparisons with 265/65R18

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.