Tire Size Box

325/40R19 vs 325/50R19

325/50R19 compared with 325/40R19

+8.8% diameter, 0.0" width

325/50R19 is 31.80" tall vs 29.24". More than the 3% rule of thumb, so check carefully before switching.

29.2"19" rim5.1"12.8" wide
325/40R19 (solid) compared with 325/50R19 (dashed outline), drawn to scale

With 325/50R19 tires, when your speedometer says 60 mph you are really going

65.3 mph

325/50R19 is +2.56 inches (+8.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/40R19325/50R19Difference%
Overall diameter29.24"31.80"+2.56"+8.8%
Section width12.80"12.80"0.00"0.0%
Sidewall height5.12"6.40"+1.28"+25.0%
Circumference91.85"99.89"+8.04"+8.8%
Revolutions per mile689.8634.3−55.5−8.0%

Speedometer difference

If your vehicle came with 325/40R19 and you fit 325/50R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.8 mph+1.8 mph
30 mph32.6 mph+2.6 mph
40 mph43.5 mph+3.5 mph
50 mph54.4 mph+4.4 mph
60 mph65.3 mph+5.3 mph
65 mph70.7 mph+5.7 mph
70 mph76.1 mph+6.1 mph
75 mph81.6 mph+6.6 mph
80 mph87.0 mph+7.0 mph

Each size on its own

Questions

Which is bigger, 325/40R19 or 325/50R19?
325/50R19 is taller by 2.56 inches (31.80" vs 29.24"). 325/40R19 is the same width.
Can I replace 325/40R19 with 325/50R19?
It is not recommended without checking carefully. The diameter difference is +8.8%, 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 325/50R19 change my speedometer?
When your speedometer reads 60 mph with 325/50R19 fitted (calibrated for 325/40R19), your real speed is 65.3 mph. Your odometer will under-count miles by about 8.8%.
Will 325/50R19 lift my vehicle?
Ride height changes by half the diameter difference: +1.28 inches of ground clearance at the axle.

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