Tire Size Box

345/35R24 vs 345/40R24

345/40R24 compared with 345/35R24

+4.1% diameter, 0.0" width

345/40R24 is 34.87" tall vs 33.51". More than the 3% rule of thumb, so check carefully before switching.

33.5"24" rim4.8"13.6" wide
345/35R24 (solid) compared with 345/40R24 (dashed outline), drawn to scale

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

62.4 mph

345/40R24 is +1.36 inches (+4.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/35R24345/40R24Difference%
Overall diameter33.51"34.87"+1.36"+4.1%
Section width13.58"13.58"0.00"0.0%
Sidewall height4.75"5.43"+0.68"+14.3%
Circumference105.27"109.54"+4.27"+4.1%
Revolutions per mile601.9578.4−23.4−3.9%

Speedometer difference

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

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph52.0 mph+2.0 mph
60 mph62.4 mph+2.4 mph
65 mph67.6 mph+2.6 mph
70 mph72.8 mph+2.8 mph
75 mph78.0 mph+3.0 mph
80 mph83.2 mph+3.2 mph

Each size on its own

Questions

Which is bigger, 345/35R24 or 345/40R24?
345/40R24 is taller by 1.36 inches (34.87" vs 33.51"). 345/35R24 is the same width.
Can I replace 345/35R24 with 345/40R24?
It is not recommended without checking carefully. The diameter difference is +4.1%, 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 345/35R24), your real speed is 62.4 mph. Your odometer will under-count miles by about 4.1%.
Will 345/40R24 lift my vehicle?
Ride height changes by half the diameter difference: +0.68 inches of ground clearance at the axle.

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