Tire Size Box

265/35R18 vs 265/45R18

265/45R18 compared with 265/35R18

+8.2% diameter, 0.0" width

265/45R18 is 27.39" tall vs 25.30". More than the 3% rule of thumb, so check carefully before switching.

25.3"18" rim3.7"10.4" wide
265/35R18 (solid) compared with 265/45R18 (dashed outline), drawn to scale

With 265/45R18 tires, when your speedometer says 60 mph you are really going

64.9 mph

265/45R18 is +2.09 inches (+8.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

265/35R18265/45R18Difference%
Overall diameter25.30"27.39"+2.09"+8.2%
Section width10.43"10.43"0.00"0.0%
Sidewall height3.65"4.69"+1.04"+28.6%
Circumference79.49"86.05"+6.56"+8.2%
Revolutions per mile797.1736.3−60.7−7.6%

Speedometer difference

If your vehicle came with 265/35R18 and you fit 265/45R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.6 mph+1.6 mph
30 mph32.5 mph+2.5 mph
40 mph43.3 mph+3.3 mph
50 mph54.1 mph+4.1 mph
60 mph64.9 mph+4.9 mph
65 mph70.4 mph+5.4 mph
70 mph75.8 mph+5.8 mph
75 mph81.2 mph+6.2 mph
80 mph86.6 mph+6.6 mph

Each size on its own

Questions

Which is bigger, 265/35R18 or 265/45R18?
265/45R18 is taller by 2.09 inches (27.39" vs 25.30"). 265/35R18 is the same width.
Can I replace 265/35R18 with 265/45R18?
It is not recommended without checking carefully. The diameter difference is +8.2%, 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 265/45R18 change my speedometer?
When your speedometer reads 60 mph with 265/45R18 fitted (calibrated for 265/35R18), your real speed is 64.9 mph. Your odometer will under-count miles by about 8.2%.
Will 265/45R18 lift my vehicle?
Ride height changes by half the diameter difference: +1.04 inches of ground clearance at the axle.

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