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235/55R19 vs 255/45R20 tire size comparison

235/55R19255/45R20

255/45R20 is 0.2 in (0.49%) shorter than 235/55R19 and 0.7 in wider. They fit different wheels: 235/55R19 a 19-inch wheel and 255/45R20 a 20-inch wheel.

235/55R19 and 255/45R20 side by side

-0.2 in / -0.49%235/55R19: 29.2 in tall, solid line255/45R20: 29.0 in tall, dashed line235/55R19Width 9.3 in (235 mm)Sidewall 5.1 in (129 mm)255/45R20Width 10.0 in (255 mm)Sidewall 4.5 in (115 mm)
235/55R19 is drawn with a solid line and 255/45R20 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 235/55R19 and 255/45R20, with the difference (255/45R20 minus 235/55R19)
Measurement235/55R19255/45R20DifferenceDifference %
Section width9.3 in (235 mm)10.0 in (255 mm)+0.7 in (+20 mm)+8.51%
Sidewall height5.1 in (129 mm)4.5 in (115 mm)-0.6 in (-14 mm)-11.22%
Wheel (rim) diameter19.0 in (483 mm)20.0 in (508 mm)+1.0 in (+25 mm)+5.26%
Overall diameter29.2 in (741 mm)29.0 in (738 mm)-0.2 in (-3 mm)-0.49%
Circumference91.7 in (2328 mm)91.2 in (2317 mm)-0.5 in (-11 mm)-0.49%
Revolutions per mile691695+4+0.49%

Differences are 255/45R20 minus 235/55R19; percentages are relative to 235/55R19. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.49%, 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 235/55R19, the actual speed on 255/45R20 is about 59.7 mph. When it reads 60 mph on a vehicle built for 255/45R20, the actual speed on 235/55R19 is about 60.3 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, 235/55R19 against 255/45R20
Speedometer readsActual on 255/45R20 (built for 235/55R19)Actual on 235/55R19 (built for 255/45R20)
20 mph19.9 mph20.1 mph
30 mph29.9 mph30.1 mph
40 mph39.8 mph40.2 mph
50 mph49.8 mph50.2 mph
60 mph59.7 mph60.3 mph
70 mph69.7 mph70.3 mph
80 mph79.6 mph80.4 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 235/55R19 or 255/45R20 tires

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Other comparisons with 235/55R19

Side-by-side dimensions and speedometer difference for sizes close to 235/55R19 in overall diameter.

Other comparisons with 255/45R20

Side-by-side dimensions and speedometer difference for sizes close to 255/45R20 in overall diameter.

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