275/45R19 vs 315/35R20

315/35R20 is 0.06 in (1.6 mm) shorter than 275/45R19, a −0.22% diameter difference. With the speedometer set for 275/45R19, an indicated 60 mph is 59.9 mph on 315/35R20.

Is this a safe swap?

Diameter difference −0.22%: under 1%

By overall diameter alone, 315/35R20 is a near match for 275/45R19; the speedometer changes by less than 1%. 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.

275/45R19 vs 315/35R20 differences
Measurement	275/45R19	315/35R20	Difference	% diff
Overall diameter	28.74 in (730.1 mm)	28.68 in (728.5 mm)	−0.06 in (−1.6 mm)	−0.22%
Sidewall height	4.87 in (123.8 mm)	4.34 in (110.3 mm)	−0.53 in (−13.5 mm)	−10.91%
Section width	10.83 in (275.0 mm)	12.40 in (315.0 mm)	+1.57 in (+40.0 mm)	+14.55%
Circumference	90.30 in (2,293.7 mm)	90.10 in (2,288.7 mm)	−0.20 in (−5.0 mm)	−0.22%
Revolutions per mile	702	703	+2	+0.22%

True speed with the speedometer calibrated for 275/45R19
Indicated	Actual on 275/45R19	Actual on 315/35R20	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.9 mph	−0.1 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 315/35R20 lowers the vehicle by 0.03 in (0.8 mm) at the axle (half the −1.6 mm diameter difference).

315/35R20 is 0.06 in shorter than 275/45R19 and 40 mm wider, a 0.22% difference in overall diameter.

With the speedometer calibrated for 275/45R19, an indicated 60 mph is actually 59.9 mph on 315/35R20, and revolutions per mile change from 702 to 703.

315/35R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 275/45R19.

Size pages

Other comparisons with 275/45R19

Other comparisons with 315/35R20

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