TireSizesFinder

305/35R19 vs 275/35R20

275/35R20 is 0.17 in (4.4 mm) taller than 305/35R19, a +0.63% diameter difference. With the speedometer set for 305/35R19, an indicated 60 mph is 60.4 mph on 275/35R20.

Is this a safe swap?

Diameter difference +0.63%: under 1%

By overall diameter alone, 275/35R20 is a near match for 305/35R19; 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: 305/35R19 (27.41 in) vs 275/35R20 (27.58 in)305/35R1927.41 in × 12.01 in275/35R2027.58 in × 10.83 in
Side profile and tread width, drawn to the same scale.
305/35R19 vs 275/35R20 differences
Measurement305/35R19275/35R20Difference% diff
Overall diameter27.41 in (696.1 mm)27.58 in (700.5 mm)+0.17 in (+4.4 mm)+0.63%
Sidewall height4.20 in (106.8 mm)3.79 in (96.3 mm)−0.41 in (−10.5 mm)−9.84%
Section width12.01 in (305.0 mm)10.83 in (275.0 mm)−1.18 in (−30.0 mm)−9.84%
Circumference86.10 in (2,186.9 mm)86.64 in (2,200.7 mm)+0.54 in (+13.8 mm)+0.63%
Revolutions per mile736731−5−0.63%
True speed with the speedometer calibrated for 305/35R19
IndicatedActual on 305/35R19Actual on 275/35R20Difference
30 mph30.0 mph30.2 mph+0.2 mph
60 mph60.0 mph60.4 mph+0.4 mph
75 mph75.0 mph75.5 mph+0.5 mph

Ride-height change: 275/35R20 raises the vehicle by 0.09 in (2.2 mm) at the axle (half the +4.4 mm diameter difference).

275/35R20 is 0.17 in taller than 305/35R19 and 30 mm narrower, a 0.63% difference in overall diameter.

With the speedometer calibrated for 305/35R19, an indicated 60 mph is actually 60.4 mph on 275/35R20, and revolutions per mile change from 736 to 731.

275/35R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 305/35R19.

Size pages

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