TireSizesFinder

315/70R18 vs 35x13.50R20

35x13.50R20 is 0.36 in (9.2 mm) shorter than 315/70R18, a −1.02% diameter difference. With the speedometer set for 315/70R18, an indicated 60 mph is 59.4 mph on 35x13.50R20.

Is this a safe swap?

Diameter difference −1.02%: within the ±3% guideline

By overall diameter alone, 35x13.50R20 falls inside the ±3% range commonly used as a guideline when replacing 315/70R18. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 315/70R18 (35.36 in) vs 35x13.50R20 (35.00 in)315/70R1835.36 in × 12.40 in35x13.50R2035.00 in × 13.50 in
Side profile and tread width, drawn to the same scale.
315/70R18 vs 35x13.50R20 differences
Measurement315/70R1835x13.50R20Difference% diff
Overall diameter35.36 in (898.2 mm)35.00 in (889.0 mm)−0.36 in (−9.2 mm)−1.02%
Sidewall height8.68 in (220.5 mm)7.50 in (190.5 mm)−1.18 in (−30.0 mm)−13.61%
Section width12.40 in (315.0 mm)13.50 in (342.9 mm)+1.10 in (+27.9 mm)+8.86%
Circumference111.09 in (2,821.8 mm)109.96 in (2,792.9 mm)−1.14 in (−28.9 mm)−1.02%
Revolutions per mile570576+6+1.03%
True speed with the speedometer calibrated for 315/70R18
IndicatedActual on 315/70R18Actual on 35x13.50R20Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.4 mph−0.6 mph
75 mph75.0 mph74.2 mph−0.8 mph

Ride-height change: 35x13.50R20 lowers the vehicle by 0.18 in (4.6 mm) at the axle (half the −9.2 mm diameter difference).

35x13.50R20 is 0.36 in shorter than 315/70R18 and 28 mm wider, a 1.02% difference in overall diameter.

With the speedometer calibrated for 315/70R18, an indicated 60 mph is actually 59.4 mph on 35x13.50R20, and revolutions per mile change from 570 to 576.

35x13.50R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 315/70R18.

Size pages

Other comparisons with 315/70R18

Other comparisons with 35x13.50R20

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