Tire Size Box

255/25R22 vs 255/30R22

255/30R22 compared with 255/25R22

+3.7% diameter, 0.0" width

255/30R22 is 28.02" tall vs 27.02". More than the 3% rule of thumb, so check carefully before switching.

27.0"22" rim2.5"10.0" wide
255/25R22 (solid) compared with 255/30R22 (dashed outline), drawn to scale

With 255/30R22 tires, when your speedometer says 60 mph you are really going

62.2 mph

255/30R22 is +1.00 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/25R22255/30R22Difference%
Overall diameter27.02"28.02"+1.00"+3.7%
Section width10.04"10.04"0.00"0.0%
Sidewall height2.51"3.01"+0.50"+20.0%
Circumference84.88"88.04"+3.15"+3.7%
Revolutions per mile746.4719.7−26.7−3.6%

Speedometer difference

If your vehicle came with 255/25R22 and you fit 255/30R22, 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, 255/25R22 or 255/30R22?
255/30R22 is taller by 1.00 inches (28.02" vs 27.02"). 255/25R22 is the same width.
Can I replace 255/25R22 with 255/30R22?
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 255/30R22 change my speedometer?
When your speedometer reads 60 mph with 255/30R22 fitted (calibrated for 255/25R22), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 255/30R22 lift my vehicle?
Ride height changes by half the diameter difference: +0.50 inches of ground clearance at the axle.

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