Tire Size Box

315/40R19 vs 315/50R19

315/50R19 compared with 315/40R19

+8.6% diameter, 0.0" width

315/50R19 is 31.40" tall vs 28.92". More than the 3% rule of thumb, so check carefully before switching.

28.9"19" rim5.0"12.4" wide
315/40R19 (solid) compared with 315/50R19 (dashed outline), drawn to scale

With 315/50R19 tires, when your speedometer says 60 mph you are really going

65.1 mph

315/50R19 is +2.48 inches (+8.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/40R19315/50R19Difference%
Overall diameter28.92"31.40"+2.48"+8.6%
Section width12.40"12.40"0.00"0.0%
Sidewall height4.96"6.20"+1.24"+25.0%
Circumference90.86"98.65"+7.79"+8.6%
Revolutions per mile697.3642.3−55.1−7.9%

Speedometer difference

If your vehicle came with 315/40R19 and you fit 315/50R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.7 mph+1.7 mph
30 mph32.6 mph+2.6 mph
40 mph43.4 mph+3.4 mph
50 mph54.3 mph+4.3 mph
60 mph65.1 mph+5.1 mph
65 mph70.6 mph+5.6 mph
70 mph76.0 mph+6.0 mph
75 mph81.4 mph+6.4 mph
80 mph86.9 mph+6.9 mph

Each size on its own

Questions

Which is bigger, 315/40R19 or 315/50R19?
315/50R19 is taller by 2.48 inches (31.40" vs 28.92"). 315/40R19 is the same width.
Can I replace 315/40R19 with 315/50R19?
It is not recommended without checking carefully. The diameter difference is +8.6%, 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 315/50R19 change my speedometer?
When your speedometer reads 60 mph with 315/50R19 fitted (calibrated for 315/40R19), your real speed is 65.1 mph. Your odometer will under-count miles by about 8.6%.
Will 315/50R19 lift my vehicle?
Ride height changes by half the diameter difference: +1.24 inches of ground clearance at the axle.

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