Tire Size Box

325/30R20 vs 325/35R20

325/35R20 compared with 325/30R20

+4.6% diameter, 0.0" width

325/35R20 is 28.96" tall vs 27.68". More than the 3% rule of thumb, so check carefully before switching.

27.7"20" rim3.8"12.8" wide
325/30R20 (solid) compared with 325/35R20 (dashed outline), drawn to scale

With 325/35R20 tires, when your speedometer says 60 mph you are really going

62.8 mph

325/35R20 is +1.28 inches (+4.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/30R20325/35R20Difference%
Overall diameter27.68"28.96"+1.28"+4.6%
Section width12.80"12.80"0.00"0.0%
Sidewall height3.84"4.48"+0.64"+16.7%
Circumference86.95"90.97"+4.02"+4.6%
Revolutions per mile728.7696.5−32.2−4.4%

Speedometer difference

If your vehicle came with 325/30R20 and you fit 325/35R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.4 mph+1.4 mph
40 mph41.8 mph+1.8 mph
50 mph52.3 mph+2.3 mph
60 mph62.8 mph+2.8 mph
65 mph68.0 mph+3.0 mph
70 mph73.2 mph+3.2 mph
75 mph78.5 mph+3.5 mph
80 mph83.7 mph+3.7 mph

Each size on its own

Questions

Which is bigger, 325/30R20 or 325/35R20?
325/35R20 is taller by 1.28 inches (28.96" vs 27.68"). 325/30R20 is the same width.
Can I replace 325/30R20 with 325/35R20?
It is not recommended without checking carefully. The diameter difference is +4.6%, 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 325/35R20 change my speedometer?
When your speedometer reads 60 mph with 325/35R20 fitted (calibrated for 325/30R20), your real speed is 62.8 mph. Your odometer will under-count miles by about 4.6%.
Will 325/35R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.64 inches of ground clearance at the axle.

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