Tire Size Box

305/45R22 vs 305/55R22

305/55R22 compared with 305/45R22

+7.3% diameter, 0.0" width

305/55R22 is 35.21" tall vs 32.81". More than the 3% rule of thumb, so check carefully before switching.

32.8"22" rim5.4"12.0" wide
305/45R22 (solid) compared with 305/55R22 (dashed outline), drawn to scale

With 305/55R22 tires, when your speedometer says 60 mph you are really going

64.4 mph

305/55R22 is +2.40 inches (+7.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

305/45R22305/55R22Difference%
Overall diameter32.81"35.21"+2.40"+7.3%
Section width12.01"12.01"0.00"0.0%
Sidewall height5.40"6.60"+1.20"+22.2%
Circumference103.07"110.61"+7.54"+7.3%
Revolutions per mile614.7572.8−41.9−6.8%

Speedometer difference

If your vehicle came with 305/45R22 and you fit 305/55R22, 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 mph42.9 mph+2.9 mph
50 mph53.7 mph+3.7 mph
60 mph64.4 mph+4.4 mph
65 mph69.8 mph+4.8 mph
70 mph75.1 mph+5.1 mph
75 mph80.5 mph+5.5 mph
80 mph85.9 mph+5.9 mph

Each size on its own

Questions

Which is bigger, 305/45R22 or 305/55R22?
305/55R22 is taller by 2.40 inches (35.21" vs 32.81"). 305/45R22 is the same width.
Can I replace 305/45R22 with 305/55R22?
It is not recommended without checking carefully. The diameter difference is +7.3%, 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 305/55R22 change my speedometer?
When your speedometer reads 60 mph with 305/55R22 fitted (calibrated for 305/45R22), your real speed is 64.4 mph. Your odometer will under-count miles by about 7.3%.
Will 305/55R22 lift my vehicle?
Ride height changes by half the diameter difference: +1.20 inches of ground clearance at the axle.

Other comparisons