315/70R17 tire size

A 315/70R17 tire is 34.36 inches (872.8 mm) tall, 12.40 in (315 mm) wide and fits a 17-inch wheel. In inch notation it is roughly a 34.4x12.4R17 — a "34-inch" tire.

315/70R17 dimensions
Overall diameter	34.36 in	872.8 mm
Section width	12.40 in	315 mm
Sidewall height	8.68 in	220.5 mm
Circumference	107.95 in	2,742 mm
Revolutions	586.9 per mile	364.7 per km
Rim diameter	17 in	431.8 mm

Compare 315/70R17 with another size

Current size

New size

Speed in mphkm/h

Overall diameter difference

−2.61%

60 mph on the speedometer = 58.4 mph actual

Within the ±3 % diameter range most tire fitters accept.

Ground clearance: −11.4 mm (−0.45 in)
Revolutions: 587 → 603 per mile

315/70R17 285/60R20

Side-by-side dimensions

	Current	New	Difference	%
Diameter	34.36 in	33.46 in	−0.90 in	−2.61%
Diameter	872.8 mm	850.0 mm	−22.8 mm	−2.61%
Width	12.40 in	11.22 in	−1.18 in	−9.52%
Width	315.0 mm	285.0 mm	−30.0 mm	−9.52%
Sidewall	8.68 in	6.73 in	−1.95 in	−22.45%
Sidewall	220.5 mm	171.0 mm	−49.5 mm	−22.45%
Circumference	107.95 in	105.13 in	−2.82 in	−2.61%
Revs per mile	586.9	602.7	+15.7	+2.68%

Speedometer error

Speedometer shows	Actual speed	Difference
20 mph	19.5 mph	−0.5 mph
30 mph	29.2 mph	−0.8 mph
40 mph	39.0 mph	−1.0 mph
50 mph	48.7 mph	−1.3 mph
60 mph	58.4 mph	−1.6 mph
70 mph	68.2 mph	−1.8 mph
80 mph	77.9 mph	−2.1 mph

Plus and minus sizes for 315/70R17

Size	Wheel	Diameter	Difference
285/60R20	Plus 3 (20 in)	33.46 in	−2.61%

Reading the 315/70R17 size

315 — section width in millimetres (12.40 in).
70 — aspect ratio: the sidewall is 70 % of the width, 220.5 mm.
R — radial construction (ZR on the sidewall means a high-speed rated radial; the dimensions are the same).
17 — fits a 17-inch diameter wheel.

The load index and speed rating (for example 91V) follow the size on the sidewall. They must meet at least the values on your vehicle's tire placard.