Tire Size Box

355/35R19 vs 345/40R19

345/40R19 compared with 355/35R19

+3.8% diameter, −0.4" width

345/40R19 is 29.87" tall vs 28.78". More than the 3% rule of thumb, so check carefully before switching.

28.8"19" rim4.9"14.0" wide
355/35R19 (solid) compared with 345/40R19 (dashed outline), drawn to scale

With 345/40R19 tires, when your speedometer says 60 mph you are really going

62.3 mph

345/40R19 is +1.08 inches (+3.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

355/35R19345/40R19Difference%
Overall diameter28.78"29.87"+1.08"+3.8%
Section width13.98"13.58"−0.39"−2.8%
Sidewall height4.89"5.43"+0.54"+11.1%
Circumference90.43"93.83"+3.40"+3.8%
Revolutions per mile700.7675.3−25.4−3.6%

Speedometer difference

If your vehicle came with 355/35R19 and you fit 345/40R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.3 mph+2.3 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph83.0 mph+3.0 mph

Each size on its own

Questions

Which is bigger, 355/35R19 or 345/40R19?
345/40R19 is taller by 1.08 inches (29.87" vs 28.78"). 355/35R19 is wider by 0.39 inches.
Can I replace 355/35R19 with 345/40R19?
It is not recommended without checking carefully. The diameter difference is +3.8%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 345/40R19 change my speedometer?
When your speedometer reads 60 mph with 345/40R19 fitted (calibrated for 355/35R19), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.8%.
Will 345/40R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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