Tire Size Box

215/35R20 vs 215/40R20

215/40R20 compared with 215/35R20

+3.3% diameter, 0.0" width

215/40R20 is 26.77" tall vs 25.93". More than the 3% rule of thumb, so check carefully before switching.

25.9"20" rim3.0"8.5" wide
215/35R20 (solid) compared with 215/40R20 (dashed outline), drawn to scale

With 215/40R20 tires, when your speedometer says 60 mph you are really going

62.0 mph

215/40R20 is +0.85 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

215/35R20215/40R20Difference%
Overall diameter25.93"26.77"+0.85"+3.3%
Section width8.46"8.46"0.00"0.0%
Sidewall height2.96"3.39"+0.42"+14.3%
Circumference81.45"84.11"+2.66"+3.3%
Revolutions per mile777.9753.3−24.6−3.2%

Speedometer difference

If your vehicle came with 215/35R20 and you fit 215/40R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph62.0 mph+2.0 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 215/35R20 or 215/40R20?
215/40R20 is taller by 0.85 inches (26.77" vs 25.93"). 215/35R20 is the same width.
Can I replace 215/35R20 with 215/40R20?
It is not recommended without checking carefully. The diameter difference is +3.3%, 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 215/40R20 change my speedometer?
When your speedometer reads 60 mph with 215/40R20 fitted (calibrated for 215/35R20), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 215/40R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.42 inches of ground clearance at the axle.

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