Tire Size Box

315/35R19 vs 315/40R19

315/40R19 compared with 315/35R19

+4.5% diameter, 0.0" width

315/40R19 is 28.92" tall vs 27.68". More than the 3% rule of thumb, so check carefully before switching.

27.7"19" rim4.3"12.4" wide
315/35R19 (solid) compared with 315/40R19 (dashed outline), drawn to scale

With 315/40R19 tires, when your speedometer says 60 mph you are really going

62.7 mph

315/40R19 is +1.24 inches (+4.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/35R19315/40R19Difference%
Overall diameter27.68"28.92"+1.24"+4.5%
Section width12.40"12.40"0.00"0.0%
Sidewall height4.34"4.96"+0.62"+14.3%
Circumference86.96"90.86"+3.90"+4.5%
Revolutions per mile728.6697.3−31.2−4.3%

Speedometer difference

If your vehicle came with 315/35R19 and you fit 315/40R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.3 mph+1.3 mph
40 mph41.8 mph+1.8 mph
50 mph52.2 mph+2.2 mph
60 mph62.7 mph+2.7 mph
65 mph67.9 mph+2.9 mph
70 mph73.1 mph+3.1 mph
75 mph78.4 mph+3.4 mph
80 mph83.6 mph+3.6 mph

Each size on its own

Questions

Which is bigger, 315/35R19 or 315/40R19?
315/40R19 is taller by 1.24 inches (28.92" vs 27.68"). 315/35R19 is the same width.
Can I replace 315/35R19 with 315/40R19?
It is not recommended without checking carefully. The diameter difference is +4.5%, 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 315/40R19 change my speedometer?
When your speedometer reads 60 mph with 315/40R19 fitted (calibrated for 315/35R19), your real speed is 62.7 mph. Your odometer will under-count miles by about 4.5%.
Will 315/40R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

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