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255/60R20 vs LT275/65R18 tire size comparison

255/60R20LT275/65R18

LT275/65R18 is 0.1 in (0.09%) taller than 255/60R20 and 0.8 in wider. They fit different wheels: 255/60R20 a 20-inch wheel and LT275/65R18 an 18-inch wheel.

255/60R20 and LT275/65R18 side by side

+0.1 in / +0.09%255/60R20: 32.0 in tall, solid lineLT275/65R18: 32.1 in tall, dashed line255/60R20Width 10.0 in (255 mm)Sidewall 6.0 in (153 mm)LT275/65R18Width 10.8 in (275 mm)Sidewall 7.0 in (179 mm)
255/60R20 is drawn with a solid line and LT275/65R18 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 255/60R20 and LT275/65R18, with the difference (LT275/65R18 minus 255/60R20)
Measurement255/60R20LT275/65R18DifferenceDifference %
Section width10.0 in (255 mm)10.8 in (275 mm)+0.8 in (+20 mm)+7.84%
Sidewall height6.0 in (153 mm)7.0 in (179 mm)+1.0 in (+26 mm)+16.83%
Wheel (rim) diameter20.0 in (508 mm)18.0 in (457 mm)-2.0 in (-51 mm)-10.00%
Overall diameter32.0 in (814 mm)32.1 in (815 mm)+0.1 in (+1 mm)+0.09%
Circumference100.7 in (2557 mm)100.8 in (2559 mm)+0.1 in (+2 mm)+0.09%
Revolutions per mile6296290-0.09%

Differences are LT275/65R18 minus 255/60R20; percentages are relative to 255/60R20. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.09%, 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 255/60R20, the actual speed on LT275/65R18 is about 60.1 mph. When it reads 60 mph on a vehicle built for LT275/65R18, the actual speed on 255/60R20 is about 59.9 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, 255/60R20 against LT275/65R18
Speedometer readsActual on LT275/65R18 (built for 255/60R20)Actual on 255/60R20 (built for LT275/65R18)
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 mph60.1 mph59.9 mph
70 mph70.1 mph69.9 mph
80 mph80.1 mph79.9 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 255/60R20 or LT275/65R18 tires

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Other comparisons with 255/60R20

Side-by-side dimensions and speedometer difference for sizes close to 255/60R20 in overall diameter.

Other comparisons with LT275/65R18

Side-by-side dimensions and speedometer difference for sizes close to LT275/65R18 in overall diameter.

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