TireSizesFinder

30x9.50R15 vs 235/70R17

235/70R17 is 0.05 in (1.2 mm) shorter than 30x9.50R15, a −0.16% diameter difference. With the speedometer set for 30x9.50R15, an indicated 60 mph is 59.9 mph on 235/70R17.

Is this a safe swap?

Diameter difference −0.16%: under 1%

By overall diameter alone, 235/70R17 is a near match for 30x9.50R15; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 30x9.50R15 (30.00 in) vs 235/70R17 (29.95 in)30x9.50R1530.00 in × 9.50 in235/70R1729.95 in × 9.25 in
Side profile and tread width, drawn to the same scale.
30x9.50R15 vs 235/70R17 differences
Measurement30x9.50R15235/70R17Difference% diff
Overall diameter30.00 in (762.0 mm)29.95 in (760.8 mm)−0.05 in (−1.2 mm)−0.16%
Sidewall height7.50 in (190.5 mm)6.48 in (164.5 mm)−1.02 in (−26.0 mm)−13.65%
Section width9.50 in (241.3 mm)9.25 in (235.0 mm)−0.25 in (−6.3 mm)−2.61%
Circumference94.25 in (2,393.9 mm)94.10 in (2,390.1 mm)−0.15 in (−3.8 mm)−0.16%
Revolutions per mile672673+1+0.16%
True speed with the speedometer calibrated for 30x9.50R15
IndicatedActual on 30x9.50R15Actual on 235/70R17Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph59.9 mph−0.1 mph
75 mph75.0 mph74.9 mph−0.1 mph

Ride-height change: 235/70R17 lowers the vehicle by 0.02 in (0.6 mm) at the axle (half the −1.2 mm diameter difference).

235/70R17 is 0.05 in shorter than 30x9.50R15 and 6 mm narrower, a 0.16% difference in overall diameter.

With the speedometer calibrated for 30x9.50R15, an indicated 60 mph is actually 59.9 mph on 235/70R17, and revolutions per mile change from 672 to 673.

235/70R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 30x9.50R15.

Size pages

Other comparisons with 30x9.50R15

Other comparisons with 235/70R17

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