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275/70R18 vs 285/40R24 tire size comparison

275/70R18285/40R24

285/40R24 is 0.2 in (0.55%) shorter than 275/70R18 and 0.4 in wider. They fit different wheels: 275/70R18 an 18-inch wheel and 285/40R24 a 24-inch wheel.

275/70R18 and 285/40R24 side by side

-0.2 in / -0.55%275/70R18: 33.2 in tall, solid line285/40R24: 33.0 in tall, dashed line275/70R18Width 10.8 in (275 mm)Sidewall 7.6 in (193 mm)285/40R24Width 11.2 in (285 mm)Sidewall 4.5 in (114 mm)
275/70R18 is drawn with a solid line and 285/40R24 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 275/70R18 and 285/40R24, with the difference (285/40R24 minus 275/70R18)
Measurement275/70R18285/40R24DifferenceDifference %
Section width10.8 in (275 mm)11.2 in (285 mm)+0.4 in (+10 mm)+3.64%
Sidewall height7.6 in (193 mm)4.5 in (114 mm)-3.1 in (-79 mm)-40.78%
Wheel (rim) diameter18.0 in (457 mm)24.0 in (610 mm)+6.0 in (+153 mm)+33.33%
Overall diameter33.2 in (842 mm)33.0 in (838 mm)-0.2 in (-4 mm)-0.55%
Circumference104.2 in (2646 mm)103.6 in (2631 mm)-0.6 in (-15 mm)-0.55%
Revolutions per mile608612+4+0.55%

Differences are 285/40R24 minus 275/70R18; percentages are relative to 275/70R18. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.55%, 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 275/70R18, the actual speed on 285/40R24 is about 59.7 mph. When it reads 60 mph on a vehicle built for 285/40R24, the actual speed on 275/70R18 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, 275/70R18 against 285/40R24
Speedometer readsActual on 285/40R24 (built for 275/70R18)Actual on 275/70R18 (built for 285/40R24)
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 275/70R18 or 285/40R24 tires

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Other comparisons with 275/70R18

Side-by-side dimensions and speedometer difference for sizes close to 275/70R18 in overall diameter.

Other comparisons with 285/40R24

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

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