Tire Size Box

235/35R17 vs 235/45R17

235/45R17 compared with 235/35R17

+7.9% diameter, 0.0" width

235/45R17 is 25.33" tall vs 23.48". More than the 3% rule of thumb, so check carefully before switching.

23.5"17" rim3.2"9.3" wide
235/35R17 (solid) compared with 235/45R17 (dashed outline), drawn to scale

With 235/45R17 tires, when your speedometer says 60 mph you are really going

64.7 mph

235/45R17 is +1.85 inches (+7.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/35R17235/45R17Difference%
Overall diameter23.48"25.33"+1.85"+7.9%
Section width9.25"9.25"0.00"0.0%
Sidewall height3.24"4.16"+0.93"+28.6%
Circumference73.75"79.57"+5.81"+7.9%
Revolutions per mile859.1796.3−62.8−7.3%

Speedometer difference

If your vehicle came with 235/35R17 and you fit 235/45R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.6 mph+1.6 mph
30 mph32.4 mph+2.4 mph
40 mph43.2 mph+3.2 mph
50 mph53.9 mph+3.9 mph
60 mph64.7 mph+4.7 mph
65 mph70.1 mph+5.1 mph
70 mph75.5 mph+5.5 mph
75 mph80.9 mph+5.9 mph
80 mph86.3 mph+6.3 mph

Each size on its own

Questions

Which is bigger, 235/35R17 or 235/45R17?
235/45R17 is taller by 1.85 inches (25.33" vs 23.48"). 235/35R17 is the same width.
Can I replace 235/35R17 with 235/45R17?
It is not recommended without checking carefully. The diameter difference is +7.9%, 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 235/45R17 change my speedometer?
When your speedometer reads 60 mph with 235/45R17 fitted (calibrated for 235/35R17), your real speed is 64.7 mph. Your odometer will under-count miles by about 7.9%.
Will 235/45R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.93 inches of ground clearance at the axle.

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