Tire Size Box

275/45R15 vs 275/55R15

275/55R15 compared with 275/45R15

+8.8% diameter, 0.0" width

275/55R15 is 26.91" tall vs 24.74". More than the 3% rule of thumb, so check carefully before switching.

24.7"15" rim4.9"10.8" wide
275/45R15 (solid) compared with 275/55R15 (dashed outline), drawn to scale

With 275/55R15 tires, when your speedometer says 60 mph you are really going

65.3 mph

275/55R15 is +2.17 inches (+8.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/45R15275/55R15Difference%
Overall diameter24.74"26.91"+2.17"+8.8%
Section width10.83"10.83"0.00"0.0%
Sidewall height4.87"5.95"+1.08"+22.2%
Circumference77.74"84.54"+6.80"+8.8%
Revolutions per mile815.1749.5−65.6−8.0%

Speedometer difference

If your vehicle came with 275/45R15 and you fit 275/55R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.8 mph+1.8 mph
30 mph32.6 mph+2.6 mph
40 mph43.5 mph+3.5 mph
50 mph54.4 mph+4.4 mph
60 mph65.3 mph+5.3 mph
65 mph70.7 mph+5.7 mph
70 mph76.1 mph+6.1 mph
75 mph81.6 mph+6.6 mph
80 mph87.0 mph+7.0 mph

Each size on its own

Questions

Which is bigger, 275/45R15 or 275/55R15?
275/55R15 is taller by 2.17 inches (26.91" vs 24.74"). 275/45R15 is the same width.
Can I replace 275/45R15 with 275/55R15?
It is not recommended without checking carefully. The diameter difference is +8.8%, 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 275/55R15 change my speedometer?
When your speedometer reads 60 mph with 275/55R15 fitted (calibrated for 275/45R15), your real speed is 65.3 mph. Your odometer will under-count miles by about 8.8%.
Will 275/55R15 lift my vehicle?
Ride height changes by half the diameter difference: +1.08 inches of ground clearance at the axle.

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