Tire Size Box

335/30R21 vs 325/35R21

325/35R21 compared with 335/30R21

+3.6% diameter, −0.4" width

325/35R21 is 29.96" tall vs 28.91". More than the 3% rule of thumb, so check carefully before switching.

28.9"21" rim4.0"13.2" wide
335/30R21 (solid) compared with 325/35R21 (dashed outline), drawn to scale

With 325/35R21 tires, when your speedometer says 60 mph you are really going

62.2 mph

325/35R21 is +1.04 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

335/30R21325/35R21Difference%
Overall diameter28.91"29.96"+1.04"+3.6%
Section width13.19"12.80"−0.39"−3.0%
Sidewall height3.96"4.48"+0.52"+13.2%
Circumference90.83"94.11"+3.28"+3.6%
Revolutions per mile697.5673.2−24.3−3.5%

Speedometer difference

If your vehicle came with 335/30R21 and you fit 325/35R21, 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 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.7 mph+2.7 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 335/30R21 or 325/35R21?
325/35R21 is taller by 1.04 inches (29.96" vs 28.91"). 335/30R21 is wider by 0.39 inches.
Can I replace 335/30R21 with 325/35R21?
It is not recommended without checking carefully. The diameter difference is +3.6%, 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 325/35R21 change my speedometer?
When your speedometer reads 60 mph with 325/35R21 fitted (calibrated for 335/30R21), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 325/35R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.52 inches of ground clearance at the axle.

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