Tire Size Box

225/35R20 vs 225/45R20

225/45R20 compared with 225/35R20

+6.8% diameter, 0.0" width

225/45R20 is 27.97" tall vs 26.20". More than the 3% rule of thumb, so check carefully before switching.

26.2"20" rim3.1"8.9" wide
225/35R20 (solid) compared with 225/45R20 (dashed outline), drawn to scale

With 225/45R20 tires, when your speedometer says 60 mph you are really going

64.1 mph

225/45R20 is +1.77 inches (+6.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/35R20225/45R20Difference%
Overall diameter26.20"27.97"+1.77"+6.8%
Section width8.86"8.86"0.00"0.0%
Sidewall height3.10"3.99"+0.89"+28.6%
Circumference82.31"87.88"+5.57"+6.8%
Revolutions per mile769.8721.0−48.8−6.3%

Speedometer difference

If your vehicle came with 225/35R20 and you fit 225/45R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.0 mph+2.0 mph
40 mph42.7 mph+2.7 mph
50 mph53.4 mph+3.4 mph
60 mph64.1 mph+4.1 mph
65 mph69.4 mph+4.4 mph
70 mph74.7 mph+4.7 mph
75 mph80.1 mph+5.1 mph
80 mph85.4 mph+5.4 mph

Each size on its own

Questions

Which is bigger, 225/35R20 or 225/45R20?
225/45R20 is taller by 1.77 inches (27.97" vs 26.20"). 225/35R20 is the same width.
Can I replace 225/35R20 with 225/45R20?
It is not recommended without checking carefully. The diameter difference is +6.8%, 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 225/45R20 change my speedometer?
When your speedometer reads 60 mph with 225/45R20 fitted (calibrated for 225/35R20), your real speed is 64.1 mph. Your odometer will under-count miles by about 6.8%.
Will 225/45R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.89 inches of ground clearance at the axle.

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