Tire Size Box

295/25R20 vs 295/30R20

295/30R20 compared with 295/25R20

+4.5% diameter, 0.0" width

295/30R20 is 26.97" 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 295/30R20 (dashed outline), drawn to scale

With 295/30R20 tires, when your speedometer says 60 mph you are really going

62.7 mph

295/30R20 is +1.16 inches (+4.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/25R20295/30R20Difference%
Overall diameter25.81"26.97"+1.16"+4.5%
Section width11.61"11.61"0.00"0.0%
Sidewall height2.90"3.48"+0.58"+20.0%
Circumference81.08"84.72"+3.65"+4.5%
Revolutions per mile781.5747.8−33.7−4.3%

Speedometer difference

If your vehicle came with 295/25R20 and you fit 295/30R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.4 mph+1.4 mph
40 mph41.8 mph+1.8 mph
50 mph52.3 mph+2.3 mph
60 mph62.7 mph+2.7 mph
65 mph67.9 mph+2.9 mph
70 mph73.2 mph+3.2 mph
75 mph78.4 mph+3.4 mph
80 mph83.6 mph+3.6 mph

Each size on its own

Questions

Which is bigger, 295/25R20 or 295/30R20?
295/30R20 is taller by 1.16 inches (26.97" vs 25.81"). 295/25R20 is the same width.
Can I replace 295/25R20 with 295/30R20?
It is not recommended without checking carefully. The diameter difference is +4.5%, 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 295/30R20 change my speedometer?
When your speedometer reads 60 mph with 295/30R20 fitted (calibrated for 295/25R20), your real speed is 62.7 mph. Your odometer will under-count miles by about 4.5%.
Will 295/30R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.58 inches of ground clearance at the axle.

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