225/75R15 vs 245/75R15

245/75R15 is 1.18 in (30.0 mm) taller than 225/75R15, a +4.18% diameter difference. With the speedometer set for 225/75R15, an indicated 60 mph is 62.5 mph on 245/75R15.

Is this a safe swap?

Diameter difference +4.18%: outside the ±3% guideline

By overall diameter alone, 245/75R15 falls outside the ±3% range commonly used as a guideline when replacing 225/75R15; speedometer and ride-height changes are larger. 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.

225/75R15 vs 245/75R15 differences
Measurement	225/75R15	245/75R15	Difference	% diff
Overall diameter	28.29 in (718.5 mm)	29.47 in (748.5 mm)	+1.18 in (+30.0 mm)	+4.18%
Sidewall height	6.64 in (168.8 mm)	7.23 in (183.8 mm)	+0.59 in (+15.0 mm)	+8.89%
Section width	8.86 in (225.0 mm)	9.65 in (245.0 mm)	+0.79 in (+20.0 mm)	+8.89%
Circumference	88.87 in (2,257.2 mm)	92.58 in (2,351.5 mm)	+3.71 in (+94.2 mm)	+4.18%
Revolutions per mile	713	684	−29	−4.01%

True speed with the speedometer calibrated for 225/75R15
Indicated	Actual on 225/75R15	Actual on 245/75R15	Difference
30 mph	30.0 mph	31.3 mph	+1.3 mph
60 mph	60.0 mph	62.5 mph	+2.5 mph
75 mph	75.0 mph	78.1 mph	+3.1 mph

Ride-height change: 245/75R15 raises the vehicle by 0.59 in (15.0 mm) at the axle (half the +30.0 mm diameter difference).

245/75R15 is 1.18 in taller than 225/75R15 and 20 mm wider, a 4.18% difference in overall diameter.

With the speedometer calibrated for 225/75R15, an indicated 60 mph is actually 62.5 mph on 245/75R15, and revolutions per mile change from 713 to 684.

Both sizes mount on 15-inch wheels.

Size pages

Other comparisons with 225/75R15

Other comparisons with 245/75R15

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