315/70R17 vs 315/75R17

315/75R17 is 1.24 in (31.5 mm) taller than 315/70R17, a +3.61% diameter difference. With the speedometer set for 315/70R17, an indicated 60 mph is 62.2 mph on 315/75R17.

Is this a safe swap?

Diameter difference +3.61%: outside the ±3% guideline

By overall diameter alone, 315/75R17 falls outside the ±3% range commonly used as a guideline when replacing 315/70R17; 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.

315/70R17 vs 315/75R17 differences
Measurement	315/70R17	315/75R17	Difference	% diff
Overall diameter	34.36 in (872.8 mm)	35.60 in (904.3 mm)	+1.24 in (+31.5 mm)	+3.61%
Sidewall height	8.68 in (220.5 mm)	9.30 in (236.3 mm)	+0.62 in (+15.8 mm)	+7.14%
Section width	12.40 in (315.0 mm)	12.40 in (315.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	107.95 in (2,742.0 mm)	111.85 in (2,840.9 mm)	+3.90 in (+99.0 mm)	+3.61%
Revolutions per mile	587	566	−20	−3.48%

True speed with the speedometer calibrated for 315/70R17
Indicated	Actual on 315/70R17	Actual on 315/75R17	Difference
30 mph	30.0 mph	31.1 mph	+1.1 mph
60 mph	60.0 mph	62.2 mph	+2.2 mph
75 mph	75.0 mph	77.7 mph	+2.7 mph

Ride-height change: 315/75R17 raises the vehicle by 0.62 in (15.8 mm) at the axle (half the +31.5 mm diameter difference).

315/75R17 is 1.24 in taller than 315/70R17 and the same width, a 3.61% difference in overall diameter.

With the speedometer calibrated for 315/70R17, an indicated 60 mph is actually 62.2 mph on 315/75R17, and revolutions per mile change from 587 to 566.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 315/70R17

Other comparisons with 315/75R17

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