Tire Size Box

345/30R21 vs 335/35R21

335/35R21 compared with 345/30R21

+3.7% diameter, −0.4" width

335/35R21 is 30.23" tall vs 29.15". More than the 3% rule of thumb, so check carefully before switching.

29.1"21" rim4.1"13.6" wide
345/30R21 (solid) compared with 335/35R21 (dashed outline), drawn to scale

With 335/35R21 tires, when your speedometer says 60 mph you are really going

62.2 mph

335/35R21 is +1.08 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/30R21335/35R21Difference%
Overall diameter29.15"30.23"+1.08"+3.7%
Section width13.58"13.19"−0.39"−2.9%
Sidewall height4.07"4.62"+0.54"+13.3%
Circumference91.58"94.98"+3.40"+3.7%
Revolutions per mile691.9667.1−24.8−3.6%

Speedometer difference

If your vehicle came with 345/30R21 and you fit 335/35R21, 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, 345/30R21 or 335/35R21?
335/35R21 is taller by 1.08 inches (30.23" vs 29.15"). 345/30R21 is wider by 0.39 inches.
Can I replace 345/30R21 with 335/35R21?
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 335/35R21 change my speedometer?
When your speedometer reads 60 mph with 335/35R21 fitted (calibrated for 345/30R21), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 335/35R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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