Tire Size Box

215/25R20 vs 215/30R20

215/30R20 compared with 215/25R20

+3.5% diameter, 0.0" width

215/30R20 is 25.08" tall vs 24.23". More than the 3% rule of thumb, so check carefully before switching.

24.2"20" rim2.1"8.5" wide
215/25R20 (solid) compared with 215/30R20 (dashed outline), drawn to scale

With 215/30R20 tires, when your speedometer says 60 mph you are really going

62.1 mph

215/30R20 is +0.85 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

215/25R20215/30R20Difference%
Overall diameter24.23"25.08"+0.85"+3.5%
Section width8.46"8.46"0.00"0.0%
Sidewall height2.12"2.54"+0.42"+20.0%
Circumference76.13"78.79"+2.66"+3.5%
Revolutions per mile832.3804.2−28.1−3.4%

Speedometer difference

If your vehicle came with 215/25R20 and you fit 215/30R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.4 mph+1.4 mph
50 mph51.7 mph+1.7 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.4 mph+2.4 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 215/25R20 or 215/30R20?
215/30R20 is taller by 0.85 inches (25.08" vs 24.23"). 215/25R20 is the same width.
Can I replace 215/25R20 with 215/30R20?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 215/30R20 change my speedometer?
When your speedometer reads 60 mph with 215/30R20 fitted (calibrated for 215/25R20), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 215/30R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.42 inches of ground clearance at the axle.

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