TireSizesFinder

35x12.50R17 vs 315/70R18

315/70R18 is 0.36 in (9.2 mm) taller than 35x12.50R17, a +1.03% diameter difference. With the speedometer set for 35x12.50R17, an indicated 60 mph is 60.6 mph on 315/70R18.

Is this a safe swap?

Diameter difference +1.03%: within the ±3% guideline

By overall diameter alone, 315/70R18 falls inside the ±3% range commonly used as a guideline when replacing 35x12.50R17. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 35x12.50R17 (35.00 in) vs 315/70R18 (35.36 in)35x12.50R1735.00 in × 12.50 in315/70R1835.36 in × 12.40 in
Side profile and tread width, drawn to the same scale.
35x12.50R17 vs 315/70R18 differences
Measurement35x12.50R17315/70R18Difference% diff
Overall diameter35.00 in (889.0 mm)35.36 in (898.2 mm)+0.36 in (+9.2 mm)+1.03%
Sidewall height9.00 in (228.6 mm)8.68 in (220.5 mm)−0.32 in (−8.1 mm)−3.54%
Section width12.50 in (317.5 mm)12.40 in (315.0 mm)−0.10 in (−2.5 mm)−0.79%
Circumference109.96 in (2,792.9 mm)111.09 in (2,821.8 mm)+1.14 in (+28.9 mm)+1.03%
Revolutions per mile576570−6−1.02%
True speed with the speedometer calibrated for 35x12.50R17
IndicatedActual on 35x12.50R17Actual on 315/70R18Difference
30 mph30.0 mph30.3 mph+0.3 mph
60 mph60.0 mph60.6 mph+0.6 mph
75 mph75.0 mph75.8 mph+0.8 mph

Ride-height change: 315/70R18 raises the vehicle by 0.18 in (4.6 mm) at the axle (half the +9.2 mm diameter difference).

315/70R18 is 0.36 in taller than 35x12.50R17 and 3 mm narrower, a 1.03% difference in overall diameter.

With the speedometer calibrated for 35x12.50R17, an indicated 60 mph is actually 60.6 mph on 315/70R18, and revolutions per mile change from 576 to 570.

315/70R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 35x12.50R17.

Size pages

Other comparisons with 35x12.50R17

Other comparisons with 315/70R18

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