Tire Size Box

245/35R17 vs 245/45R17

245/45R17 compared with 245/35R17

+8.1% diameter, 0.0" width

245/45R17 is 25.68" tall vs 23.75". More than the 3% rule of thumb, so check carefully before switching.

23.8"17" rim3.4"9.6" wide
245/35R17 (solid) compared with 245/45R17 (dashed outline), drawn to scale

With 245/45R17 tires, when your speedometer says 60 mph you are really going

64.9 mph

245/45R17 is +1.93 inches (+8.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

245/35R17245/45R17Difference%
Overall diameter23.75"25.68"+1.93"+8.1%
Section width9.65"9.65"0.00"0.0%
Sidewall height3.38"4.34"+0.96"+28.6%
Circumference74.62"80.68"+6.06"+8.1%
Revolutions per mile849.1785.3−63.8−7.5%

Speedometer difference

If your vehicle came with 245/35R17 and you fit 245/45R17, 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 mph54.1 mph+4.1 mph
60 mph64.9 mph+4.9 mph
65 mph70.3 mph+5.3 mph
70 mph75.7 mph+5.7 mph
75 mph81.1 mph+6.1 mph
80 mph86.5 mph+6.5 mph

Each size on its own

Questions

Which is bigger, 245/35R17 or 245/45R17?
245/45R17 is taller by 1.93 inches (25.68" vs 23.75"). 245/35R17 is the same width.
Can I replace 245/35R17 with 245/45R17?
It is not recommended without checking carefully. The diameter difference is +8.1%, 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 245/45R17 change my speedometer?
When your speedometer reads 60 mph with 245/45R17 fitted (calibrated for 245/35R17), your real speed is 64.9 mph. Your odometer will under-count miles by about 8.1%.
Will 245/45R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.96 inches of ground clearance at the axle.

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