Tire Size Box

345/35R19 vs 345/40R19

345/40R19 compared with 345/35R19

+4.8% diameter, 0.0" width

345/40R19 is 29.87" tall vs 28.51". More than the 3% rule of thumb, so check carefully before switching.

28.5"19" rim4.8"13.6" wide
345/35R19 (solid) compared with 345/40R19 (dashed outline), drawn to scale

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

62.9 mph

345/40R19 is +1.36 inches (+4.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/35R19345/40R19Difference%
Overall diameter28.51"29.87"+1.36"+4.8%
Section width13.58"13.58"0.00"0.0%
Sidewall height4.75"5.43"+0.68"+14.3%
Circumference89.56"93.83"+4.27"+4.8%
Revolutions per mile707.5675.3−32.2−4.5%

Speedometer difference

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

Speedometer showsActual speedDifference
20 mph21.0 mph+1.0 mph
30 mph31.4 mph+1.4 mph
40 mph41.9 mph+1.9 mph
50 mph52.4 mph+2.4 mph
60 mph62.9 mph+2.9 mph
65 mph68.1 mph+3.1 mph
70 mph73.3 mph+3.3 mph
75 mph78.6 mph+3.6 mph
80 mph83.8 mph+3.8 mph

Each size on its own

Questions

Which is bigger, 345/35R19 or 345/40R19?
345/40R19 is taller by 1.36 inches (29.87" vs 28.51"). 345/35R19 is the same width.
Can I replace 345/35R19 with 345/40R19?
It is not recommended without checking carefully. The diameter difference is +4.8%, 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 345/35R19), your real speed is 62.9 mph. Your odometer will under-count miles by about 4.8%.
Will 345/40R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.68 inches of ground clearance at the axle.

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