Tire Size Box

235/85R16 vs 255/85R16

255/85R16 compared with 235/85R16

+4.2% diameter, +0.8" width

255/85R16 is 33.07" tall vs 31.73". More than the 3% rule of thumb, so check carefully before switching.

31.7"16" rim7.9"9.3" wide
235/85R16 (solid) compared with 255/85R16 (dashed outline), drawn to scale

With 255/85R16 tires, when your speedometer says 60 mph you are really going

62.5 mph

255/85R16 is +1.34 inches (+4.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/85R16255/85R16Difference%
Overall diameter31.73"33.07"+1.34"+4.2%
Section width9.25"10.04"+0.79"+8.5%
Sidewall height7.86"8.53"+0.67"+8.5%
Circumference99.68"103.88"+4.21"+4.2%
Revolutions per mile635.6609.9−25.7−4.0%

Speedometer difference

If your vehicle came with 235/85R16 and you fit 255/85R16, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.3 mph+1.3 mph
40 mph41.7 mph+1.7 mph
50 mph52.1 mph+2.1 mph
60 mph62.5 mph+2.5 mph
65 mph67.7 mph+2.7 mph
70 mph73.0 mph+3.0 mph
75 mph78.2 mph+3.2 mph
80 mph83.4 mph+3.4 mph

Each size on its own

Questions

Which is bigger, 235/85R16 or 255/85R16?
255/85R16 is taller by 1.34 inches (33.07" vs 31.73"). 255/85R16 is wider by 0.79 inches.
Can I replace 235/85R16 with 255/85R16?
It is not recommended without checking carefully. The diameter difference is +4.2%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 255/85R16 change my speedometer?
When your speedometer reads 60 mph with 255/85R16 fitted (calibrated for 235/85R16), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.2%.
Will 255/85R16 lift my vehicle?
Ride height changes by half the diameter difference: +0.67 inches of ground clearance at the axle.

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