Tire Size Box

265/35R20 vs 265/45R20

265/45R20 compared with 265/35R20

+7.6% diameter, 0.0" width

265/45R20 is 29.39" tall vs 27.30". More than the 3% rule of thumb, so check carefully before switching.

27.3"20" rim3.7"10.4" wide
265/35R20 (solid) compared with 265/45R20 (dashed outline), drawn to scale

With 265/45R20 tires, when your speedometer says 60 mph you are really going

64.6 mph

265/45R20 is +2.09 inches (+7.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

265/35R20265/45R20Difference%
Overall diameter27.30"29.39"+2.09"+7.6%
Section width10.43"10.43"0.00"0.0%
Sidewall height3.65"4.69"+1.04"+28.6%
Circumference85.78"92.33"+6.56"+7.6%
Revolutions per mile738.7686.2−52.4−7.1%

Speedometer difference

If your vehicle came with 265/35R20 and you fit 265/45R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.5 mph+1.5 mph
30 mph32.3 mph+2.3 mph
40 mph43.1 mph+3.1 mph
50 mph53.8 mph+3.8 mph
60 mph64.6 mph+4.6 mph
65 mph70.0 mph+5.0 mph
70 mph75.3 mph+5.3 mph
75 mph80.7 mph+5.7 mph
80 mph86.1 mph+6.1 mph

Each size on its own

Questions

Which is bigger, 265/35R20 or 265/45R20?
265/45R20 is taller by 2.09 inches (29.39" vs 27.30"). 265/35R20 is the same width.
Can I replace 265/35R20 with 265/45R20?
It is not recommended without checking carefully. The diameter difference is +7.6%, 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 265/45R20 change my speedometer?
When your speedometer reads 60 mph with 265/45R20 fitted (calibrated for 265/35R20), your real speed is 64.6 mph. Your odometer will under-count miles by about 7.6%.
Will 265/45R20 lift my vehicle?
Ride height changes by half the diameter difference: +1.04 inches of ground clearance at the axle.

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