Tire Size Box

295/25R20 vs 285/30R20

285/30R20 compared with 295/25R20

+3.6% diameter, −0.4" width

285/30R20 is 26.73" tall vs 25.81". More than the 3% rule of thumb, so check carefully before switching.

25.8"20" rim2.9"11.6" wide
295/25R20 (solid) compared with 285/30R20 (dashed outline), drawn to scale

With 285/30R20 tires, when your speedometer says 60 mph you are really going

62.2 mph

285/30R20 is +0.93 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/25R20285/30R20Difference%
Overall diameter25.81"26.73"+0.93"+3.6%
Section width11.61"11.22"−0.39"−3.4%
Sidewall height2.90"3.37"+0.46"+15.9%
Circumference81.08"83.98"+2.91"+3.6%
Revolutions per mile781.5754.4−27.0−3.5%

Speedometer difference

If your vehicle came with 295/25R20 and you fit 285/30R20, 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 mph67.3 mph+2.3 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, 295/25R20 or 285/30R20?
285/30R20 is taller by 0.93 inches (26.73" vs 25.81"). 295/25R20 is wider by 0.39 inches.
Can I replace 295/25R20 with 285/30R20?
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 285/30R20 change my speedometer?
When your speedometer reads 60 mph with 285/30R20 fitted (calibrated for 295/25R20), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 285/30R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.46 inches of ground clearance at the axle.

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