275/70R17 vs 265/65R18

265/65R18 is 0.59 in (15.1 mm) shorter than 275/70R17, a −1.85% diameter difference. With the speedometer set for 275/70R17, an indicated 60 mph is 58.9 mph on 265/65R18.

Is this a safe swap?

Diameter difference −1.85%: within the ±3% guideline

By overall diameter alone, 265/65R18 falls inside the ±3% range commonly used as a guideline when replacing 275/70R17. 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.

275/70R17 vs 265/65R18 differences
Measurement	275/70R17	265/65R18	Difference	% diff
Overall diameter	32.16 in (816.8 mm)	31.56 in (801.7 mm)	−0.59 in (−15.1 mm)	−1.85%
Sidewall height	7.58 in (192.5 mm)	6.78 in (172.3 mm)	−0.80 in (−20.2 mm)	−10.52%
Section width	10.83 in (275.0 mm)	10.43 in (265.0 mm)	−0.39 in (−10.0 mm)	−3.64%
Circumference	101.03 in (2,566.1 mm)	99.16 in (2,518.6 mm)	−1.87 in (−47.4 mm)	−1.85%
Revolutions per mile	627	639	+12	+1.88%

True speed with the speedometer calibrated for 275/70R17
Indicated	Actual on 275/70R17	Actual on 265/65R18	Difference
30 mph	30.0 mph	29.4 mph	−0.6 mph
60 mph	60.0 mph	58.9 mph	−1.1 mph
75 mph	75.0 mph	73.6 mph	−1.4 mph

Ride-height change: 265/65R18 lowers the vehicle by 0.30 in (7.5 mm) at the axle (half the −15.1 mm diameter difference).

265/65R18 is 0.59 in shorter than 275/70R17 and 10 mm narrower, a 1.85% difference in overall diameter.

With the speedometer calibrated for 275/70R17, an indicated 60 mph is actually 58.9 mph on 265/65R18, and revolutions per mile change from 627 to 639.

265/65R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 275/70R17.

Size pages

Other comparisons with 275/70R17

Other comparisons with 265/65R18

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