Tire Size Box

295/40R21 vs 295/50R21

295/50R21 compared with 295/40R21

+7.7% diameter, 0.0" width

295/50R21 is 32.61" tall vs 30.29". More than the 3% rule of thumb, so check carefully before switching.

30.3"21" rim4.6"11.6" wide
295/40R21 (solid) compared with 295/50R21 (dashed outline), drawn to scale

With 295/50R21 tires, when your speedometer says 60 mph you are really going

64.6 mph

295/50R21 is +2.32 inches (+7.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/40R21295/50R21Difference%
Overall diameter30.29"32.61"+2.32"+7.7%
Section width11.61"11.61"0.00"0.0%
Sidewall height4.65"5.81"+1.16"+25.0%
Circumference95.16"102.46"+7.30"+7.7%
Revolutions per mile665.8618.4−47.4−7.1%

Speedometer difference

If your vehicle came with 295/40R21 and you fit 295/50R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.5 mph+1.5 mph
30 mph32.3 mph+2.3 mph
40 mph43.1 mph+3.1 mph
50 mph53.8 mph+3.8 mph
60 mph64.6 mph+4.6 mph
65 mph70.0 mph+5.0 mph
70 mph75.4 mph+5.4 mph
75 mph80.8 mph+5.8 mph
80 mph86.1 mph+6.1 mph

Each size on its own

Questions

Which is bigger, 295/40R21 or 295/50R21?
295/50R21 is taller by 2.32 inches (32.61" vs 30.29"). 295/40R21 is the same width.
Can I replace 295/40R21 with 295/50R21?
It is not recommended without checking carefully. The diameter difference is +7.7%, 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 295/50R21 change my speedometer?
When your speedometer reads 60 mph with 295/50R21 fitted (calibrated for 295/40R21), your real speed is 64.6 mph. Your odometer will under-count miles by about 7.7%.
Will 295/50R21 lift my vehicle?
Ride height changes by half the diameter difference: +1.16 inches of ground clearance at the axle.

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