Tire Size Box

355/30R20 vs 355/35R20

355/35R20 compared with 355/30R20

+4.9% diameter, 0.0" width

355/35R20 is 29.78" tall vs 28.39". More than the 3% rule of thumb, so check carefully before switching.

28.4"20" rim4.2"14.0" wide
355/30R20 (solid) compared with 355/35R20 (dashed outline), drawn to scale

With 355/35R20 tires, when your speedometer says 60 mph you are really going

63.0 mph

355/35R20 is +1.40 inches (+4.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

355/30R20355/35R20Difference%
Overall diameter28.39"29.78"+1.40"+4.9%
Section width13.98"13.98"0.00"0.0%
Sidewall height4.19"4.89"+0.70"+16.7%
Circumference89.18"93.57"+4.39"+4.9%
Revolutions per mile710.5677.2−33.3−4.7%

Speedometer difference

If your vehicle came with 355/30R20 and you fit 355/35R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.0 mph+1.0 mph
30 mph31.5 mph+1.5 mph
40 mph42.0 mph+2.0 mph
50 mph52.5 mph+2.5 mph
60 mph63.0 mph+3.0 mph
65 mph68.2 mph+3.2 mph
70 mph73.4 mph+3.4 mph
75 mph78.7 mph+3.7 mph
80 mph83.9 mph+3.9 mph

Each size on its own

Questions

Which is bigger, 355/30R20 or 355/35R20?
355/35R20 is taller by 1.40 inches (29.78" vs 28.39"). 355/30R20 is the same width.
Can I replace 355/30R20 with 355/35R20?
It is not recommended without checking carefully. The diameter difference is +4.9%, 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 355/35R20 change my speedometer?
When your speedometer reads 60 mph with 355/35R20 fitted (calibrated for 355/30R20), your real speed is 63.0 mph. Your odometer will under-count miles by about 4.9%.
Will 355/35R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.70 inches of ground clearance at the axle.

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