TireSizesFinder

245/75R15 vs 30x9.50R15

30x9.50R15 is 0.53 in (13.5 mm) taller than 245/75R15, a +1.80% diameter difference. With the speedometer set for 245/75R15, an indicated 60 mph is 61.1 mph on 30x9.50R15.

Is this a safe swap?

Diameter difference +1.80%: within the ±3% guideline

By overall diameter alone, 30x9.50R15 falls inside the ±3% range commonly used as a guideline when replacing 245/75R15. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 245/75R15 (29.47 in) vs 30x9.50R15 (30.00 in)245/75R1529.47 in × 9.65 in30x9.50R1530.00 in × 9.50 in
Side profile and tread width, drawn to the same scale.
245/75R15 vs 30x9.50R15 differences
Measurement245/75R1530x9.50R15Difference% diff
Overall diameter29.47 in (748.5 mm)30.00 in (762.0 mm)+0.53 in (+13.5 mm)+1.80%
Sidewall height7.23 in (183.8 mm)7.50 in (190.5 mm)+0.27 in (+6.8 mm)+3.67%
Section width9.65 in (245.0 mm)9.50 in (241.3 mm)−0.15 in (−3.7 mm)−1.51%
Circumference92.58 in (2,351.5 mm)94.25 in (2,393.9 mm)+1.67 in (+42.4 mm)+1.80%
Revolutions per mile684672−12−1.77%
True speed with the speedometer calibrated for 245/75R15
IndicatedActual on 245/75R15Actual on 30x9.50R15Difference
30 mph30.0 mph30.5 mph+0.5 mph
60 mph60.0 mph61.1 mph+1.1 mph
75 mph75.0 mph76.4 mph+1.4 mph

Ride-height change: 30x9.50R15 raises the vehicle by 0.27 in (6.8 mm) at the axle (half the +13.5 mm diameter difference).

30x9.50R15 is 0.53 in taller than 245/75R15 and 4 mm narrower, a 1.80% difference in overall diameter.

With the speedometer calibrated for 245/75R15, an indicated 60 mph is actually 61.1 mph on 30x9.50R15, and revolutions per mile change from 684 to 672.

Both sizes mount on 15-inch wheels.

Size pages

Other comparisons with 245/75R15

Other comparisons with 30x9.50R15

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.