Tire Size Box

355/25R24 vs 345/30R24

345/30R24 compared with 355/25R24

+3.7% diameter, −0.4" width

345/30R24 is 32.15" tall vs 30.99". More than the 3% rule of thumb, so check carefully before switching.

31.0"24" rim3.5"14.0" wide
355/25R24 (solid) compared with 345/30R24 (dashed outline), drawn to scale

With 345/30R24 tires, when your speedometer says 60 mph you are really going

62.2 mph

345/30R24 is +1.16 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

355/25R24345/30R24Difference%
Overall diameter30.99"32.15"+1.16"+3.7%
Section width13.98"13.58"−0.39"−2.8%
Sidewall height3.49"4.07"+0.58"+16.6%
Circumference97.35"101.00"+3.65"+3.7%
Revolutions per mile650.8627.3−23.5−3.6%

Speedometer difference

If your vehicle came with 355/25R24 and you fit 345/30R24, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.2 mph+2.2 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, 355/25R24 or 345/30R24?
345/30R24 is taller by 1.16 inches (32.15" vs 30.99"). 355/25R24 is wider by 0.39 inches.
Can I replace 355/25R24 with 345/30R24?
It is not recommended without checking carefully. The diameter difference is +3.7%, 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 345/30R24 change my speedometer?
When your speedometer reads 60 mph with 345/30R24 fitted (calibrated for 355/25R24), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 345/30R24 lift my vehicle?
Ride height changes by half the diameter difference: +0.58 inches of ground clearance at the axle.

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