Tire Size Box

355/25R21 vs 355/35R21

355/35R21 compared with 355/25R21

+10.0% diameter, 0.0" width

355/35R21 is 30.78" tall vs 27.99". More than the 3% rule of thumb, so check carefully before switching.

28.0"21" rim3.5"14.0" wide
355/25R21 (solid) compared with 355/35R21 (dashed outline), drawn to scale

With 355/35R21 tires, when your speedometer says 60 mph you are really going

66.0 mph

355/35R21 is +2.80 inches (+10.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

355/25R21355/35R21Difference%
Overall diameter27.99"30.78"+2.80"+10.0%
Section width13.98"13.98"0.00"0.0%
Sidewall height3.49"4.89"+1.40"+40.0%
Circumference87.93"96.71"+8.78"+10.0%
Revolutions per mile720.6655.2−65.4−9.1%

Speedometer difference

If your vehicle came with 355/25R21 and you fit 355/35R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph22.0 mph+2.0 mph
30 mph33.0 mph+3.0 mph
40 mph44.0 mph+4.0 mph
50 mph55.0 mph+5.0 mph
60 mph66.0 mph+6.0 mph
65 mph71.5 mph+6.5 mph
70 mph77.0 mph+7.0 mph
75 mph82.5 mph+7.5 mph
80 mph88.0 mph+8.0 mph

Each size on its own

Questions

Which is bigger, 355/25R21 or 355/35R21?
355/35R21 is taller by 2.80 inches (30.78" vs 27.99"). 355/25R21 is the same width.
Can I replace 355/25R21 with 355/35R21?
It is not recommended without checking carefully. The diameter difference is +10.0%, 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 355/35R21 change my speedometer?
When your speedometer reads 60 mph with 355/35R21 fitted (calibrated for 355/25R21), your real speed is 66.0 mph. Your odometer will under-count miles by about 10.0%.
Will 355/35R21 lift my vehicle?
Ride height changes by half the diameter difference: +1.40 inches of ground clearance at the axle.

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