Tire Size Box

235/30R20 vs 235/35R20

235/35R20 compared with 235/30R20

+3.6% diameter, 0.0" width

235/35R20 is 26.48" tall vs 25.55". More than the 3% rule of thumb, so check carefully before switching.

25.6"20" rim2.8"9.3" wide
235/30R20 (solid) compared with 235/35R20 (dashed outline), drawn to scale

With 235/35R20 tires, when your speedometer says 60 mph you are really going

62.2 mph

235/35R20 is +0.93 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/30R20235/35R20Difference%
Overall diameter25.55"26.48"+0.93"+3.6%
Section width9.25"9.25"0.00"0.0%
Sidewall height2.78"3.24"+0.46"+16.7%
Circumference80.27"83.18"+2.91"+3.6%
Revolutions per mile789.3761.7−27.6−3.5%

Speedometer difference

If your vehicle came with 235/30R20 and you fit 235/35R20, 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 mph67.4 mph+2.4 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, 235/30R20 or 235/35R20?
235/35R20 is taller by 0.93 inches (26.48" vs 25.55"). 235/30R20 is the same width.
Can I replace 235/30R20 with 235/35R20?
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 235/35R20 change my speedometer?
When your speedometer reads 60 mph with 235/35R20 fitted (calibrated for 235/30R20), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 235/35R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.46 inches of ground clearance at the axle.

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