Tire Size Box

285/35R24 vs 285/40R24

285/40R24 compared with 285/35R24

+3.5% diameter, 0.0" width

285/40R24 is 32.98" tall vs 31.85". More than the 3% rule of thumb, so check carefully before switching.

31.9"24" rim3.9"11.2" wide
285/35R24 (solid) compared with 285/40R24 (dashed outline), drawn to scale

With 285/40R24 tires, when your speedometer says 60 mph you are really going

62.1 mph

285/40R24 is +1.12 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/35R24285/40R24Difference%
Overall diameter31.85"32.98"+1.12"+3.5%
Section width11.22"11.22"0.00"0.0%
Sidewall height3.93"4.49"+0.56"+14.3%
Circumference100.07"103.60"+3.53"+3.5%
Revolutions per mile633.1611.6−21.5−3.4%

Speedometer difference

If your vehicle came with 285/35R24 and you fit 285/40R24, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 285/35R24 or 285/40R24?
285/40R24 is taller by 1.12 inches (32.98" vs 31.85"). 285/35R24 is the same width.
Can I replace 285/35R24 with 285/40R24?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 285/40R24 change my speedometer?
When your speedometer reads 60 mph with 285/40R24 fitted (calibrated for 285/35R24), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 285/40R24 lift my vehicle?
Ride height changes by half the diameter difference: +0.56 inches of ground clearance at the axle.

Other comparisons