Tire Size Box

315/35R24 vs 315/40R24

315/40R24 compared with 315/35R24

+3.8% diameter, 0.0" width

315/40R24 is 33.92" tall vs 32.68". More than the 3% rule of thumb, so check carefully before switching.

32.7"24" rim4.3"12.4" wide
315/35R24 (solid) compared with 315/40R24 (dashed outline), drawn to scale

With 315/40R24 tires, when your speedometer says 60 mph you are really going

62.3 mph

315/40R24 is +1.24 inches (+3.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/35R24315/40R24Difference%
Overall diameter32.68"33.92"+1.24"+3.8%
Section width12.40"12.40"0.00"0.0%
Sidewall height4.34"4.96"+0.62"+14.3%
Circumference102.67"106.57"+3.90"+3.8%
Revolutions per mile617.1594.6−22.6−3.7%

Speedometer difference

If your vehicle came with 315/35R24 and you fit 315/40R24, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.3 mph+2.3 mph
65 mph67.5 mph+2.5 mph
70 mph72.7 mph+2.7 mph
75 mph77.8 mph+2.8 mph
80 mph83.0 mph+3.0 mph

Each size on its own

Questions

Which is bigger, 315/35R24 or 315/40R24?
315/40R24 is taller by 1.24 inches (33.92" vs 32.68"). 315/35R24 is the same width.
Can I replace 315/35R24 with 315/40R24?
It is not recommended without checking carefully. The diameter difference is +3.8%, 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 315/40R24 change my speedometer?
When your speedometer reads 60 mph with 315/40R24 fitted (calibrated for 315/35R24), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.8%.
Will 315/40R24 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

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