Tire Size Box

235/70R18 vs 275/55R19

275/55R19 compared with 235/70R18

−0.1% diameter, +1.6" width

275/55R19 is 30.91" tall vs 30.95". Within the 3% rule, so usually interchangeable.

31.0"18" rim6.5"9.3" wide
235/70R18 (solid) compared with 275/55R19 (dashed outline), drawn to scale

With 275/55R19 tires, when your speedometer says 60 mph you are really going

59.9 mph

275/55R19 is −0.04 inches (−0.1%) in overall diameter. That is within the 3% most shops and makers allow.

235/70R18275/55R19Difference%
Overall diameter30.95"30.91"−0.04"−0.1%
Section width9.25"10.83"+1.57"+17.0%
Sidewall height6.48"5.95"−0.52"−8.1%
Circumference97.24"97.10"−0.14"−0.1%
Revolutions per mile651.6652.5+0.9+0.1%

Speedometer difference

If your vehicle came with 235/70R18 and you fit 275/55R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.0 mph0.0 mph
30 mph30.0 mph0.0 mph
40 mph39.9 mph−0.1 mph
50 mph49.9 mph−0.1 mph
60 mph59.9 mph−0.1 mph
65 mph64.9 mph−0.1 mph
70 mph69.9 mph−0.1 mph
75 mph74.9 mph−0.1 mph
80 mph79.9 mph−0.1 mph

Each size on its own

Questions

Which is bigger, 235/70R18 or 275/55R19?
235/70R18 is taller by 0.04 inches (30.95" vs 30.91"). 275/55R19 is wider by 1.57 inches.
Can I replace 235/70R18 with 275/55R19?
Usually, yes. The diameter difference is −0.1%, inside the 3% rule of thumb most tire shops use. Check that the wider or taller tire clears your suspension and fenders, and that its load index meets your placard.
How much will 275/55R19 change my speedometer?
When your speedometer reads 60 mph with 275/55R19 fitted (calibrated for 235/70R18), your real speed is 59.9 mph. Your odometer will over-count miles by about 0.1%.
Will 275/55R19 lift my vehicle?
Ride height changes by half the diameter difference: −0.02 inches of ground clearance at the axle.

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