Tire Size Box

275/45R20 vs 275/50R20

275/50R20 compared with 275/45R20

+3.6% diameter, 0.0" width

275/50R20 is 30.83" tall vs 29.74". More than the 3% rule of thumb, so check carefully before switching.

29.7"20" rim4.9"10.8" wide
275/45R20 (solid) compared with 275/50R20 (dashed outline), drawn to scale

With 275/50R20 tires, when your speedometer says 60 mph you are really going

62.2 mph

275/50R20 is +1.08 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/45R20275/50R20Difference%
Overall diameter29.74"30.83"+1.08"+3.6%
Section width10.83"10.83"0.00"0.0%
Sidewall height4.87"5.41"+0.54"+11.1%
Circumference93.44"96.85"+3.40"+3.6%
Revolutions per mile678.1654.2−23.8−3.5%

Speedometer difference

If your vehicle came with 275/45R20 and you fit 275/50R20, 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 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.5 mph+2.5 mph
75 mph77.7 mph+2.7 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 275/45R20 or 275/50R20?
275/50R20 is taller by 1.08 inches (30.83" vs 29.74"). 275/45R20 is the same width.
Can I replace 275/45R20 with 275/50R20?
It is not recommended without checking carefully. The diameter difference is +3.6%, 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 275/50R20 change my speedometer?
When your speedometer reads 60 mph with 275/50R20 fitted (calibrated for 275/45R20), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 275/50R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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