Tire Size Box

245/30R20 vs 245/35R20

245/35R20 compared with 245/30R20

+3.7% diameter, 0.0" width

245/35R20 is 26.75" tall vs 25.79". More than the 3% rule of thumb, so check carefully before switching.

25.8"20" rim2.9"9.6" wide
245/30R20 (solid) compared with 245/35R20 (dashed outline), drawn to scale

With 245/35R20 tires, when your speedometer says 60 mph you are really going

62.2 mph

245/35R20 is +0.96 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

245/30R20245/35R20Difference%
Overall diameter25.79"26.75"+0.96"+3.7%
Section width9.65"9.65"0.00"0.0%
Sidewall height2.89"3.38"+0.48"+16.7%
Circumference81.01"84.04"+3.03"+3.7%
Revolutions per mile782.1753.9−28.2−3.6%

Speedometer difference

If your vehicle came with 245/30R20 and you fit 245/35R20, 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 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph83.0 mph+3.0 mph

Each size on its own

Questions

Which is bigger, 245/30R20 or 245/35R20?
245/35R20 is taller by 0.96 inches (26.75" vs 25.79"). 245/30R20 is the same width.
Can I replace 245/30R20 with 245/35R20?
It is not recommended without checking carefully. The diameter difference is +3.7%, 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 245/35R20 change my speedometer?
When your speedometer reads 60 mph with 245/35R20 fitted (calibrated for 245/30R20), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 245/35R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.48 inches of ground clearance at the axle.

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