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225/65R17 vs 255/55R18 tire size comparison

225/65R17255/55R18

255/55R18 is 0.5 in (1.85%) taller than 225/65R17 and 1.1 in wider. They fit different wheels: 225/65R17 a 17-inch wheel and 255/55R18 an 18-inch wheel.

225/65R17 and 255/55R18 side by side

+0.5 in / +1.85%225/65R17: 28.5 in tall, solid line255/55R18: 29.0 in tall, dashed line225/65R17Width 8.9 in (225 mm)Sidewall 5.8 in (146 mm)255/55R18Width 10.0 in (255 mm)Sidewall 5.5 in (140 mm)
225/65R17 is drawn with a solid line and 255/55R18 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 225/65R17 and 255/55R18, with the difference (255/55R18 minus 225/65R17)
Measurement225/65R17255/55R18DifferenceDifference %
Section width8.9 in (225 mm)10.0 in (255 mm)+1.1 in (+30 mm)+13.33%
Sidewall height5.8 in (146 mm)5.5 in (140 mm)-0.3 in (-6 mm)-4.10%
Wheel (rim) diameter17.0 in (432 mm)18.0 in (457 mm)+1.0 in (+25 mm)+5.88%
Overall diameter28.5 in (724 mm)29.0 in (738 mm)+0.5 in (+14 mm)+1.85%
Circumference89.6 in (2275 mm)91.2 in (2318 mm)+1.6 in (+43 mm)+1.85%
Revolutions per mile707694-13-1.82%

Differences are 255/55R18 minus 225/65R17; percentages are relative to 225/65R17. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 1.85%, 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 225/65R17, the actual speed on 255/55R18 is about 61.1 mph. When it reads 60 mph on a vehicle built for 255/55R18, the actual speed on 225/65R17 is about 58.9 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, 225/65R17 against 255/55R18
Speedometer readsActual on 255/55R18 (built for 225/65R17)Actual on 225/65R17 (built for 255/55R18)
20 mph20.4 mph19.6 mph
30 mph30.6 mph29.5 mph
40 mph40.7 mph39.3 mph
50 mph50.9 mph49.1 mph
60 mph61.1 mph58.9 mph
70 mph71.3 mph68.7 mph
80 mph81.5 mph78.5 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 225/65R17 or 255/55R18 tires

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Other comparisons with 225/65R17

Side-by-side dimensions and speedometer difference for sizes close to 225/65R17 in overall diameter.

Other comparisons with 255/55R18

Side-by-side dimensions and speedometer difference for sizes close to 255/55R18 in overall diameter.

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