Tire Size Box

315/40R22 vs 315/50R22

315/50R22 compared with 315/40R22

+7.8% diameter, 0.0" width

315/50R22 is 34.40" tall vs 31.92". More than the 3% rule of thumb, so check carefully before switching.

31.9"22" rim5.0"12.4" wide
315/40R22 (solid) compared with 315/50R22 (dashed outline), drawn to scale

With 315/50R22 tires, when your speedometer says 60 mph you are really going

64.7 mph

315/50R22 is +2.48 inches (+7.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/40R22315/50R22Difference%
Overall diameter31.92"34.40"+2.48"+7.8%
Section width12.40"12.40"0.00"0.0%
Sidewall height4.96"6.20"+1.24"+25.0%
Circumference100.28"108.08"+7.79"+7.8%
Revolutions per mile631.8586.3−45.6−7.2%

Speedometer difference

If your vehicle came with 315/40R22 and you fit 315/50R22, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.6 mph+1.6 mph
30 mph32.3 mph+2.3 mph
40 mph43.1 mph+3.1 mph
50 mph53.9 mph+3.9 mph
60 mph64.7 mph+4.7 mph
65 mph70.1 mph+5.1 mph
70 mph75.4 mph+5.4 mph
75 mph80.8 mph+5.8 mph
80 mph86.2 mph+6.2 mph

Each size on its own

Questions

Which is bigger, 315/40R22 or 315/50R22?
315/50R22 is taller by 2.48 inches (34.40" vs 31.92"). 315/40R22 is the same width.
Can I replace 315/40R22 with 315/50R22?
It is not recommended without checking carefully. The diameter difference is +7.8%, 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 315/50R22 change my speedometer?
When your speedometer reads 60 mph with 315/50R22 fitted (calibrated for 315/40R22), your real speed is 64.7 mph. Your odometer will under-count miles by about 7.8%.
Will 315/50R22 lift my vehicle?
Ride height changes by half the diameter difference: +1.24 inches of ground clearance at the axle.

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