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285/40R24 vs LT235/80R18 tire size comparison

285/40R24LT235/80R18

LT235/80R18 is 0.2 in (0.53%) shorter than 285/40R24 and 1.9 in narrower. They fit different wheels: 285/40R24 a 24-inch wheel and LT235/80R18 an 18-inch wheel.

285/40R24 and LT235/80R18 side by side

-0.2 in / -0.53%285/40R24: 33.0 in tall, solid lineLT235/80R18: 32.8 in tall, dashed line285/40R24Width 11.2 in (285 mm)Sidewall 4.5 in (114 mm)LT235/80R18Width 9.3 in (235 mm)Sidewall 7.4 in (188 mm)
285/40R24 is drawn with a solid line and LT235/80R18 with a dashed line. In each drawing both tires are to the same scale; the tread shoulder and bead curves are simplified. The table below has the same numbers.
Dimensions of 285/40R24 and LT235/80R18, with the difference (LT235/80R18 minus 285/40R24)
Measurement285/40R24LT235/80R18DifferenceDifference %
Section width11.2 in (285 mm)9.3 in (235 mm)-1.9 in (-50 mm)-17.54%
Sidewall height4.5 in (114 mm)7.4 in (188 mm)+2.9 in (+74 mm)+64.91%
Wheel (rim) diameter24.0 in (610 mm)18.0 in (457 mm)-6.0 in (-153 mm)-25.00%
Overall diameter33.0 in (838 mm)32.8 in (833 mm)-0.2 in (-5 mm)-0.53%
Circumference103.6 in (2631 mm)103.1 in (2618 mm)-0.5 in (-13 mm)-0.53%
Revolutions per mile612615+3+0.53%

Differences are LT235/80R18 minus 285/40R24; percentages are relative to 285/40R24. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.53%, which is within the common 3% rule of thumb.

The rule of thumb keeps a replacement size within about 3% of the original overall diameter. It covers diameter only. It is not a fit, load or safety check, because width, wheel diameter, load capacity and clearance matter too. Confirm any size change with your vehicle's owner's manual or a tire professional.

Speedometer difference

When the speedometer reads 60 mph on a vehicle built for 285/40R24, the actual speed on LT235/80R18 is about 59.7 mph. When it reads 60 mph on a vehicle built for LT235/80R18, the actual speed on 285/40R24 is about 60.3 mph. These figures assume the speedometer is accurate on the original size and use nominal dimensions, so treat them as estimates.

Actual speed for a given speedometer reading, 285/40R24 against LT235/80R18
Speedometer readsActual on LT235/80R18 (built for 285/40R24)Actual on 285/40R24 (built for LT235/80R18)
20 mph19.9 mph20.1 mph
30 mph29.8 mph30.2 mph
40 mph39.8 mph40.2 mph
50 mph49.7 mph50.3 mph
60 mph59.7 mph60.3 mph
70 mph69.6 mph70.4 mph
80 mph79.6 mph80.4 mph

A common rule of thumb is to keep a replacement size within about 3% of the original overall diameter. Check the tire placard on the driver's door jamb and your owner's manual for the sizes your vehicle was built for. Confirm any size change with your vehicle's owner's manual or a tire professional.

Which vehicles use each size?

These vehicles list the size among their verified sizes, by trim. Open one to see all of its sizes.

Check it in the calculator

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Shop for 285/40R24 or LT235/80R18 tires

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Other comparisons with 285/40R24

Side-by-side dimensions and speedometer difference for sizes close to 285/40R24 in overall diameter.

Other comparisons with LT235/80R18

Side-by-side dimensions and speedometer difference for sizes close to LT235/80R18 in overall diameter.

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