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255/65R18 vs 255/70R17 tire size comparison

255/65R18255/70R17

255/70R17 is 0.00 in (0.01%) taller than 255/65R18, with the same section width. They fit different wheels: 255/65R18 an 18-inch wheel and 255/70R17 a 17-inch wheel.

255/65R18 and 255/70R17 side by side

0.0 in / +0.01%255/65R18: 31.1 in tall, solid line255/70R17: 31.1 in tall, dashed line255/65R18Width 10.0 in (255 mm)Sidewall 6.5 in (166 mm)255/70R17Width 10.0 in (255 mm)Sidewall 7.0 in (179 mm)
255/65R18 is drawn with a solid line and 255/70R17 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 255/65R18 and 255/70R17, with the difference (255/70R17 minus 255/65R18)
Measurement255/65R18255/70R17DifferenceDifference %
Section width10.0 in (255 mm)10.0 in (255 mm)0.0 in (0 mm)0.00%
Sidewall height6.5 in (166 mm)7.0 in (179 mm)+0.5 in (+13 mm)+7.69%
Wheel (rim) diameter18.0 in (457 mm)17.0 in (432 mm)-1.0 in (-25 mm)-5.56%
Overall diameter31.1 in (789 mm)31.1 in (789 mm)0.0 in (0 mm)+0.01%
Circumference97.6 in (2478 mm)97.6 in (2478 mm)0.0 in (0 mm)+0.01%
Revolutions per mile650649-1-0.01%

Differences are 255/70R17 minus 255/65R18; percentages are relative to 255/65R18. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.01%, 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 255/65R18, the actual speed on 255/70R17 is about 60.0 mph. When it reads 60 mph on a vehicle built for 255/70R17, the actual speed on 255/65R18 is about 60.0 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, 255/65R18 against 255/70R17
Speedometer readsActual on 255/70R17 (built for 255/65R18)Actual on 255/65R18 (built for 255/70R17)
20 mph20.0 mph20.0 mph
30 mph30.0 mph30.0 mph
40 mph40.0 mph40.0 mph
50 mph50.0 mph50.0 mph
60 mph60.0 mph60.0 mph
70 mph70.0 mph70.0 mph
80 mph80.0 mph80.0 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.

Open this comparison in the calculator

Shop for 255/65R18 or 255/70R17 tires

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Other comparisons with 255/65R18

Side-by-side dimensions and speedometer difference for sizes close to 255/65R18 in overall diameter.

Other comparisons with 255/70R17

Side-by-side dimensions and speedometer difference for sizes close to 255/70R17 in overall diameter.

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