Tire Size Box

335/40R19 vs 345/35R20

345/35R20 compared with 335/40R19

−0.1% diameter, +0.4" width

345/35R20 is 29.51" tall vs 29.55". Within the 3% rule, so usually interchangeable.

29.6"19" rim5.3"13.2" wide
335/40R19 (solid) compared with 345/35R20 (dashed outline), drawn to scale

With 345/35R20 tires, when your speedometer says 60 mph you are really going

59.9 mph

345/35R20 is −0.04 inches (−0.1%) in overall diameter. That is within the 3% most shops and makers allow.

335/40R19345/35R20Difference%
Overall diameter29.55"29.51"−0.04"−0.1%
Section width13.19"13.58"+0.39"+3.0%
Sidewall height5.28"4.75"−0.52"−9.9%
Circumference92.84"92.70"−0.14"−0.1%
Revolutions per mile682.5683.5+1.0+0.1%

Speedometer difference

If your vehicle came with 335/40R19 and you fit 345/35R20, 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 mph39.9 mph−0.1 mph
50 mph49.9 mph−0.1 mph
60 mph59.9 mph−0.1 mph
65 mph64.9 mph−0.1 mph
70 mph69.9 mph−0.1 mph
75 mph74.9 mph−0.1 mph
80 mph79.9 mph−0.1 mph

Each size on its own

Questions

Which is bigger, 335/40R19 or 345/35R20?
335/40R19 is taller by 0.04 inches (29.55" vs 29.51"). 345/35R20 is wider by 0.39 inches.
Can I replace 335/40R19 with 345/35R20?
Usually, yes. The diameter difference is −0.1%, 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 345/35R20 change my speedometer?
When your speedometer reads 60 mph with 345/35R20 fitted (calibrated for 335/40R19), your real speed is 59.9 mph. Your odometer will over-count miles by about 0.1%.
Will 345/35R20 lift my vehicle?
Ride height changes by half the diameter difference: −0.02 inches of ground clearance at the axle.

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