Tire Size Box

295/35R20 vs 295/40R20

295/40R20 compared with 295/35R20

+4.1% diameter, 0.0" width

295/40R20 is 29.29" tall vs 28.13". More than the 3% rule of thumb, so check carefully before switching.

28.1"20" rim4.1"11.6" wide
295/35R20 (solid) compared with 295/40R20 (dashed outline), drawn to scale

With 295/40R20 tires, when your speedometer says 60 mph you are really going

62.5 mph

295/40R20 is +1.16 inches (+4.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/35R20295/40R20Difference%
Overall diameter28.13"29.29"+1.16"+4.1%
Section width11.61"11.61"0.00"0.0%
Sidewall height4.06"4.65"+0.58"+14.3%
Circumference88.37"92.02"+3.65"+4.1%
Revolutions per mile717.0688.5−28.4−4.0%

Speedometer difference

If your vehicle came with 295/35R20 and you fit 295/40R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.7 mph+1.7 mph
50 mph52.1 mph+2.1 mph
60 mph62.5 mph+2.5 mph
65 mph67.7 mph+2.7 mph
70 mph72.9 mph+2.9 mph
75 mph78.1 mph+3.1 mph
80 mph83.3 mph+3.3 mph

Each size on its own

Questions

Which is bigger, 295/35R20 or 295/40R20?
295/40R20 is taller by 1.16 inches (29.29" vs 28.13"). 295/35R20 is the same width.
Can I replace 295/35R20 with 295/40R20?
It is not recommended without checking carefully. The diameter difference is +4.1%, 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 295/40R20 change my speedometer?
When your speedometer reads 60 mph with 295/40R20 fitted (calibrated for 295/35R20), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.1%.
Will 295/40R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.58 inches of ground clearance at the axle.

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