285/30R24 vs 305/30R24

305/30R24 is 0.47 in (12.0 mm) taller than 285/30R24, a +1.54% diameter difference. With the speedometer set for 285/30R24, an indicated 60 mph is 60.9 mph on 305/30R24.

Is this a safe swap?

Diameter difference +1.54%: within the ±3% guideline

By overall diameter alone, 305/30R24 falls inside the ±3% range commonly used as a guideline when replacing 285/30R24. 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.

285/30R24 vs 305/30R24 differences
Measurement	285/30R24	305/30R24	Difference	% diff
Overall diameter	30.73 in (780.6 mm)	31.20 in (792.6 mm)	+0.47 in (+12.0 mm)	+1.54%
Sidewall height	3.37 in (85.5 mm)	3.60 in (91.5 mm)	+0.24 in (+6.0 mm)	+7.02%
Section width	11.22 in (285.0 mm)	12.01 in (305.0 mm)	+0.79 in (+20.0 mm)	+7.02%
Circumference	96.55 in (2,452.3 mm)	98.03 in (2,490.0 mm)	+1.48 in (+37.7 mm)	+1.54%
Revolutions per mile	656	646	−10	−1.51%

True speed with the speedometer calibrated for 285/30R24
Indicated	Actual on 285/30R24	Actual on 305/30R24	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: 305/30R24 raises the vehicle by 0.24 in (6.0 mm) at the axle (half the +12.0 mm diameter difference).

305/30R24 is 0.47 in taller than 285/30R24 and 20 mm wider, a 1.54% difference in overall diameter.

With the speedometer calibrated for 285/30R24, an indicated 60 mph is actually 60.9 mph on 305/30R24, and revolutions per mile change from 656 to 646.

Both sizes mount on 24-inch wheels.

Size pages

Other comparisons with 285/30R24

Other comparisons with 305/30R24

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