Tire Size Box

295/45R21 vs 295/55R21

295/55R21 compared with 295/45R21

+7.4% diameter, 0.0" width

295/55R21 is 33.78" tall vs 31.45". More than the 3% rule of thumb, so check carefully before switching.

31.5"21" rim5.2"11.6" wide
295/45R21 (solid) compared with 295/55R21 (dashed outline), drawn to scale

With 295/55R21 tires, when your speedometer says 60 mph you are really going

64.4 mph

295/55R21 is +2.32 inches (+7.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/45R21295/55R21Difference%
Overall diameter31.45"33.78"+2.32"+7.4%
Section width11.61"11.61"0.00"0.0%
Sidewall height5.23"6.39"+1.16"+22.2%
Circumference98.81"106.11"+7.30"+7.4%
Revolutions per mile641.2597.1−44.1−6.9%

Speedometer difference

If your vehicle came with 295/45R21 and you fit 295/55R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.5 mph+1.5 mph
30 mph32.2 mph+2.2 mph
40 mph43.0 mph+3.0 mph
50 mph53.7 mph+3.7 mph
60 mph64.4 mph+4.4 mph
65 mph69.8 mph+4.8 mph
70 mph75.2 mph+5.2 mph
75 mph80.5 mph+5.5 mph
80 mph85.9 mph+5.9 mph

Each size on its own

Questions

Which is bigger, 295/45R21 or 295/55R21?
295/55R21 is taller by 2.32 inches (33.78" vs 31.45"). 295/45R21 is the same width.
Can I replace 295/45R21 with 295/55R21?
It is not recommended without checking carefully. The diameter difference is +7.4%, 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 295/55R21 change my speedometer?
When your speedometer reads 60 mph with 295/55R21 fitted (calibrated for 295/45R21), your real speed is 64.4 mph. Your odometer will under-count miles by about 7.4%.
Will 295/55R21 lift my vehicle?
Ride height changes by half the diameter difference: +1.16 inches of ground clearance at the axle.

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