Tire Size Box

285/65R19 vs 345/50R20

345/50R20 compared with 285/65R19

0.0% diameter, +2.4" width

345/50R20 is 33.58" tall vs 33.59". Within the 3% rule, so usually interchangeable.

33.6"19" rim7.3"11.2" wide
285/65R19 (solid) compared with 345/50R20 (dashed outline), drawn to scale

With 345/50R20 tires, when your speedometer says 60 mph you are really going

60.0 mph

345/50R20 is 0.00 inches (0.0%) in overall diameter. That is within the 3% most shops and makers allow.

285/65R19345/50R20Difference%
Overall diameter33.59"33.58"0.00"0.0%
Section width11.22"13.58"+2.36"+21.1%
Sidewall height7.29"6.79"−0.50"−6.9%
Circumference105.52"105.50"−0.01"0.0%
Revolutions per mile600.5600.6+0.10.0%

Speedometer difference

If your vehicle came with 285/65R19 and you fit 345/50R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.0 mph0.0 mph
30 mph30.0 mph0.0 mph
40 mph40.0 mph0.0 mph
50 mph50.0 mph0.0 mph
60 mph60.0 mph0.0 mph
65 mph65.0 mph0.0 mph
70 mph70.0 mph0.0 mph
75 mph75.0 mph0.0 mph
80 mph80.0 mph0.0 mph

Each size on its own

Questions

Which is bigger, 285/65R19 or 345/50R20?
They are the same overall diameter, 33.59 inches.
Can I replace 285/65R19 with 345/50R20?
Usually, yes. The diameter difference is 0.0%, inside the 3% rule of thumb most tire shops use. Check that the wider or taller tire clears your suspension and fenders, and that its load index meets your placard.
How much will 345/50R20 change my speedometer?
When your speedometer reads 60 mph with 345/50R20 fitted (calibrated for 285/65R19), your real speed is 60.0 mph. Your odometer will over-count miles by about 0.0%.
Will 345/50R20 lift my vehicle?
Ride height changes by half the diameter difference: 0.00 inches of ground clearance at the axle.

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