Tire Size Box

355/35R24 vs 345/40R24

345/40R24 compared with 355/35R24

+3.2% diameter, −0.4" width

345/40R24 is 34.87" tall vs 33.78". More than the 3% rule of thumb, so check carefully before switching.

33.8"24" rim4.9"14.0" wide
355/35R24 (solid) compared with 345/40R24 (dashed outline), drawn to scale

With 345/40R24 tires, when your speedometer says 60 mph you are really going

61.9 mph

345/40R24 is +1.08 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

355/35R24345/40R24Difference%
Overall diameter33.78"34.87"+1.08"+3.2%
Section width13.98"13.58"−0.39"−2.8%
Sidewall height4.89"5.43"+0.54"+11.1%
Circumference106.13"109.54"+3.40"+3.2%
Revolutions per mile597.0578.4−18.5−3.1%

Speedometer difference

If your vehicle came with 355/35R24 and you fit 345/40R24, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.1 mph+2.1 mph
70 mph72.2 mph+2.2 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 355/35R24 or 345/40R24?
345/40R24 is taller by 1.08 inches (34.87" vs 33.78"). 355/35R24 is wider by 0.39 inches.
Can I replace 355/35R24 with 345/40R24?
It is not recommended without checking carefully. The diameter difference is +3.2%, 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 345/40R24 change my speedometer?
When your speedometer reads 60 mph with 345/40R24 fitted (calibrated for 355/35R24), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 345/40R24 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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