TireSizesFinder

35x12.50R18 vs 315/60R20

315/60R20 is 0.12 in (3.0 mm) shorter than 35x12.50R18, a −0.34% diameter difference. With the speedometer set for 35x12.50R18, an indicated 60 mph is 59.8 mph on 315/60R20.

Is this a safe swap?

Diameter difference −0.34%: under 1%

By overall diameter alone, 315/60R20 is a near match for 35x12.50R18; 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: 35x12.50R18 (35.00 in) vs 315/60R20 (34.88 in)35x12.50R1835.00 in × 12.50 in315/60R2034.88 in × 12.40 in
Side profile and tread width, drawn to the same scale.
35x12.50R18 vs 315/60R20 differences
Measurement35x12.50R18315/60R20Difference% diff
Overall diameter35.00 in (889.0 mm)34.88 in (886.0 mm)−0.12 in (−3.0 mm)−0.34%
Sidewall height8.50 in (215.9 mm)7.44 in (189.0 mm)−1.06 in (−26.9 mm)−12.46%
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)109.58 in (2,783.5 mm)−0.37 in (−9.4 mm)−0.34%
Revolutions per mile576578+2+0.34%
True speed with the speedometer calibrated for 35x12.50R18
IndicatedActual on 35x12.50R18Actual on 315/60R20Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.8 mph−0.2 mph
75 mph75.0 mph74.7 mph−0.3 mph

Ride-height change: 315/60R20 lowers the vehicle by 0.06 in (1.5 mm) at the axle (half the −3.0 mm diameter difference).

315/60R20 is 0.12 in shorter than 35x12.50R18 and 3 mm narrower, a 0.34% difference in overall diameter.

With the speedometer calibrated for 35x12.50R18, an indicated 60 mph is actually 59.8 mph on 315/60R20, and revolutions per mile change from 576 to 578.

315/60R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 35x12.50R18.

Size pages

Other comparisons with 35x12.50R18

Other comparisons with 315/60R20

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