Tire Size Box

195/35R18 vs 195/45R18

195/45R18 compared with 195/35R18

+6.6% diameter, 0.0" width

195/45R18 is 24.91" tall vs 23.37". More than the 3% rule of thumb, so check carefully before switching.

23.4"18" rim2.7"7.7" wide
195/35R18 (solid) compared with 195/45R18 (dashed outline), drawn to scale

With 195/45R18 tires, when your speedometer says 60 mph you are really going

63.9 mph

195/45R18 is +1.54 inches (+6.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

195/35R18195/45R18Difference%
Overall diameter23.37"24.91"+1.54"+6.6%
Section width7.68"7.68"0.00"0.0%
Sidewall height2.69"3.45"+0.77"+28.6%
Circumference73.43"78.26"+4.82"+6.6%
Revolutions per mile862.8809.7−53.2−6.2%

Speedometer difference

If your vehicle came with 195/35R18 and you fit 195/45R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.3 mph+1.3 mph
30 mph32.0 mph+2.0 mph
40 mph42.6 mph+2.6 mph
50 mph53.3 mph+3.3 mph
60 mph63.9 mph+3.9 mph
65 mph69.3 mph+4.3 mph
70 mph74.6 mph+4.6 mph
75 mph79.9 mph+4.9 mph
80 mph85.3 mph+5.3 mph

Each size on its own

Questions

Which is bigger, 195/35R18 or 195/45R18?
195/45R18 is taller by 1.54 inches (24.91" vs 23.37"). 195/35R18 is the same width.
Can I replace 195/35R18 with 195/45R18?
It is not recommended without checking carefully. The diameter difference is +6.6%, 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 195/45R18 change my speedometer?
When your speedometer reads 60 mph with 195/45R18 fitted (calibrated for 195/35R18), your real speed is 63.9 mph. Your odometer will under-count miles by about 6.6%.
Will 195/45R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.77 inches of ground clearance at the axle.

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