305/65R17 vs 285/70R17

285/70R17 is 0.10 in (2.5 mm) taller than 305/65R17, a +0.30% diameter difference. With the speedometer set for 305/65R17, an indicated 60 mph is 60.2 mph on 285/70R17.

Is this a safe swap?

Diameter difference +0.30%: under 1%

By overall diameter alone, 285/70R17 is a near match for 305/65R17; the speedometer changes by less than 1%. 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.

305/65R17 vs 285/70R17 differences
Measurement	305/65R17	285/70R17	Difference	% diff
Overall diameter	32.61 in (828.3 mm)	32.71 in (830.8 mm)	+0.10 in (+2.5 mm)	+0.30%
Sidewall height	7.81 in (198.3 mm)	7.85 in (199.5 mm)	+0.05 in (+1.3 mm)	+0.63%
Section width	12.01 in (305.0 mm)	11.22 in (285.0 mm)	−0.79 in (−20.0 mm)	−6.56%
Circumference	102.45 in (2,602.2 mm)	102.76 in (2,610.0 mm)	+0.31 in (+7.9 mm)	+0.30%
Revolutions per mile	618	617	−2	−0.30%

True speed with the speedometer calibrated for 305/65R17
Indicated	Actual on 305/65R17	Actual on 285/70R17	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 285/70R17 raises the vehicle by 0.05 in (1.3 mm) at the axle (half the +2.5 mm diameter difference).

285/70R17 is 0.10 in taller than 305/65R17 and 20 mm narrower, a 0.30% difference in overall diameter.

With the speedometer calibrated for 305/65R17, an indicated 60 mph is actually 60.2 mph on 285/70R17, and revolutions per mile change from 618 to 617.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 305/65R17

Other comparisons with 285/70R17

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