Tire Size Box

345/25R20 vs 345/35R20

345/35R20 compared with 345/25R20

+10.1% diameter, 0.0" width

345/35R20 is 29.51" tall vs 26.79". More than the 3% rule of thumb, so check carefully before switching.

26.8"20" rim3.4"13.6" wide
345/25R20 (solid) compared with 345/35R20 (dashed outline), drawn to scale

With 345/35R20 tires, when your speedometer says 60 mph you are really going

66.1 mph

345/35R20 is +2.72 inches (+10.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/25R20345/35R20Difference%
Overall diameter26.79"29.51"+2.72"+10.1%
Section width13.58"13.58"0.00"0.0%
Sidewall height3.40"4.75"+1.36"+40.0%
Circumference84.17"92.70"+8.53"+10.1%
Revolutions per mile752.8683.5−69.3−9.2%

Speedometer difference

If your vehicle came with 345/25R20 and you fit 345/35R20, 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 mph44.1 mph+4.1 mph
50 mph55.1 mph+5.1 mph
60 mph66.1 mph+6.1 mph
65 mph71.6 mph+6.6 mph
70 mph77.1 mph+7.1 mph
75 mph82.6 mph+7.6 mph
80 mph88.1 mph+8.1 mph

Each size on its own

Questions

Which is bigger, 345/25R20 or 345/35R20?
345/35R20 is taller by 2.72 inches (29.51" vs 26.79"). 345/25R20 is the same width.
Can I replace 345/25R20 with 345/35R20?
It is not recommended without checking carefully. The diameter difference is +10.1%, 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 345/35R20 change my speedometer?
When your speedometer reads 60 mph with 345/35R20 fitted (calibrated for 345/25R20), your real speed is 66.1 mph. Your odometer will under-count miles by about 10.1%.
Will 345/35R20 lift my vehicle?
Ride height changes by half the diameter difference: +1.36 inches of ground clearance at the axle.

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