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275/55R20 vs LT255/75R17 tire size comparison

275/55R20LT255/75R17

LT255/75R17 is 0.2 in (0.47%) taller than 275/55R20 and 0.8 in narrower. They fit different wheels: 275/55R20 a 20-inch wheel and LT255/75R17 a 17-inch wheel.

275/55R20 and LT255/75R17 side by side

+0.2 in / +0.47%275/55R20: 31.9 in tall, solid lineLT255/75R17: 32.1 in tall, dashed line275/55R20Width 10.8 in (275 mm)Sidewall 6.0 in (151 mm)LT255/75R17Width 10.0 in (255 mm)Sidewall 7.5 in (191 mm)
275/55R20 is drawn with a solid line and LT255/75R17 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 275/55R20 and LT255/75R17, with the difference (LT255/75R17 minus 275/55R20)
Measurement275/55R20LT255/75R17DifferenceDifference %
Section width10.8 in (275 mm)10.0 in (255 mm)-0.8 in (-20 mm)-7.27%
Sidewall height6.0 in (151 mm)7.5 in (191 mm)+1.5 in (+40 mm)+26.45%
Wheel (rim) diameter20.0 in (508 mm)17.0 in (432 mm)-3.0 in (-76 mm)-15.00%
Overall diameter31.9 in (811 mm)32.1 in (814 mm)+0.2 in (+3 mm)+0.47%
Circumference100.2 in (2546 mm)100.7 in (2558 mm)+0.5 in (+12 mm)+0.47%
Revolutions per mile632629-3-0.47%

Differences are LT255/75R17 minus 275/55R20; percentages are relative to 275/55R20. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.47%, 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 275/55R20, the actual speed on LT255/75R17 is about 60.3 mph. When it reads 60 mph on a vehicle built for LT255/75R17, the actual speed on 275/55R20 is about 59.7 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, 275/55R20 against LT255/75R17
Speedometer readsActual on LT255/75R17 (built for 275/55R20)Actual on 275/55R20 (built for LT255/75R17)
20 mph20.1 mph19.9 mph
30 mph30.1 mph29.9 mph
40 mph40.2 mph39.8 mph
50 mph50.2 mph49.8 mph
60 mph60.3 mph59.7 mph
70 mph70.3 mph69.7 mph
80 mph80.4 mph79.6 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 275/55R20 or LT255/75R17 tires

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Other comparisons with 275/55R20

Side-by-side dimensions and speedometer difference for sizes close to 275/55R20 in overall diameter.

Other comparisons with LT255/75R17

Side-by-side dimensions and speedometer difference for sizes close to LT255/75R17 in overall diameter.

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