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235/35R19 vs 235/40R18 tire size comparison

235/35R19235/40R18

235/40R18 is 0.1 in (0.29%) shorter than 235/35R19, with the same section width. They fit different wheels: 235/35R19 a 19-inch wheel and 235/40R18 an 18-inch wheel.

235/35R19 and 235/40R18 side by side

-0.1 in / -0.29%235/35R19: 25.5 in tall, solid line235/40R18: 25.4 in tall, dashed line235/35R19Width 9.3 in (235 mm)Sidewall 3.2 in (82 mm)235/40R18Width 9.3 in (235 mm)Sidewall 3.7 in (94 mm)
235/35R19 is drawn with a solid line and 235/40R18 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 235/35R19 and 235/40R18, with the difference (235/40R18 minus 235/35R19)
Measurement235/35R19235/40R18DifferenceDifference %
Section width9.3 in (235 mm)9.3 in (235 mm)0.0 in (0 mm)0.00%
Sidewall height3.2 in (82 mm)3.7 in (94 mm)+0.5 in (+12 mm)+14.29%
Wheel (rim) diameter19.0 in (483 mm)18.0 in (457 mm)-1.0 in (-26 mm)-5.26%
Overall diameter25.5 in (647 mm)25.4 in (645 mm)-0.1 in (-2 mm)-0.29%
Circumference80.0 in (2033 mm)79.8 in (2027 mm)-0.2 in (-6 mm)-0.29%
Revolutions per mile792794+2+0.29%

Differences are 235/40R18 minus 235/35R19; percentages are relative to 235/35R19. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.29%, 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 235/35R19, the actual speed on 235/40R18 is about 59.8 mph. When it reads 60 mph on a vehicle built for 235/40R18, the actual speed on 235/35R19 is about 60.2 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, 235/35R19 against 235/40R18
Speedometer readsActual on 235/40R18 (built for 235/35R19)Actual on 235/35R19 (built for 235/40R18)
20 mph19.9 mph20.1 mph
30 mph29.9 mph30.1 mph
40 mph39.9 mph40.1 mph
50 mph49.9 mph50.1 mph
60 mph59.8 mph60.2 mph
70 mph69.8 mph70.2 mph
80 mph79.8 mph80.2 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

The calculator takes the same two sizes and shows the full comparison, or lets you swap either one for another size.

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Shop for 235/35R19 or 235/40R18 tires

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Other comparisons with 235/35R19

Side-by-side dimensions and speedometer difference for sizes close to 235/35R19 in overall diameter.

Other comparisons with 235/40R18

Side-by-side dimensions and speedometer difference for sizes close to 235/40R18 in overall diameter.

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