35x12.50R15 vs 315/75R17

315/75R17 is 0.60 in (15.3 mm) taller than 35x12.50R15, a +1.72% diameter difference. With the speedometer set for 35x12.50R15, an indicated 60 mph is 61.0 mph on 315/75R17.

Is this a safe swap?

Diameter difference +1.72%: within the ±3% guideline

By overall diameter alone, 315/75R17 falls inside the ±3% range commonly used as a guideline when replacing 35x12.50R15. 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.

35x12.50R15 vs 315/75R17 differences
Measurement	35x12.50R15	315/75R17	Difference	% diff
Overall diameter	35.00 in (889.0 mm)	35.60 in (904.3 mm)	+0.60 in (+15.3 mm)	+1.72%
Sidewall height	10.00 in (254.0 mm)	9.30 in (236.3 mm)	−0.70 in (−17.7 mm)	−6.99%
Section width	12.50 in (317.5 mm)	12.40 in (315.0 mm)	−0.10 in (−2.5 mm)	−0.79%
Circumference	109.96 in (2,792.9 mm)	111.85 in (2,840.9 mm)	+1.89 in (+48.1 mm)	+1.72%
Revolutions per mile	576	566	−10	−1.69%

True speed with the speedometer calibrated for 35x12.50R15
Indicated	Actual on 35x12.50R15	Actual on 315/75R17	Difference
30 mph	30.0 mph	30.5 mph	+0.5 mph
60 mph	60.0 mph	61.0 mph	+1.0 mph
75 mph	75.0 mph	76.3 mph	+1.3 mph

Ride-height change: 315/75R17 raises the vehicle by 0.30 in (7.6 mm) at the axle (half the +15.3 mm diameter difference).

315/75R17 is 0.60 in taller than 35x12.50R15 and 3 mm narrower, a 1.72% difference in overall diameter.

With the speedometer calibrated for 35x12.50R15, an indicated 60 mph is actually 61.0 mph on 315/75R17, and revolutions per mile change from 576 to 566.

315/75R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 35x12.50R15.

Size pages

Other comparisons with 35x12.50R15

Other comparisons with 315/75R17

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