Tire Size Box

225/25R20 vs 225/30R20

225/30R20 compared with 225/25R20

+3.6% diameter, 0.0" width

225/30R20 is 25.31" tall vs 24.43". More than the 3% rule of thumb, so check carefully before switching.

24.4"20" rim2.2"8.9" wide
225/25R20 (solid) compared with 225/30R20 (dashed outline), drawn to scale

With 225/30R20 tires, when your speedometer says 60 mph you are really going

62.2 mph

225/30R20 is +0.89 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/25R20225/30R20Difference%
Overall diameter24.43"25.31"+0.89"+3.6%
Section width8.86"8.86"0.00"0.0%
Sidewall height2.21"2.66"+0.44"+20.0%
Circumference76.75"79.53"+2.78"+3.6%
Revolutions per mile825.6796.7−28.9−3.5%

Speedometer difference

If your vehicle came with 225/25R20 and you fit 225/30R20, 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 mph41.5 mph+1.5 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, 225/25R20 or 225/30R20?
225/30R20 is taller by 0.89 inches (25.31" vs 24.43"). 225/25R20 is the same width.
Can I replace 225/25R20 with 225/30R20?
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 225/30R20 change my speedometer?
When your speedometer reads 60 mph with 225/30R20 fitted (calibrated for 225/25R20), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 225/30R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.44 inches of ground clearance at the axle.

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