Tire Size Box

235/80R16 vs 235/85R16

235/85R16 compared with 235/80R16

+3.0% diameter, 0.0" width

235/85R16 is 31.73" tall vs 30.80". More than the 3% rule of thumb, so check carefully before switching.

30.8"16" rim7.4"9.3" wide
235/80R16 (solid) compared with 235/85R16 (dashed outline), drawn to scale

With 235/85R16 tires, when your speedometer says 60 mph you are really going

61.8 mph

235/85R16 is +0.93 inches (+3.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/80R16235/85R16Difference%
Overall diameter30.80"31.73"+0.93"+3.0%
Section width9.25"9.25"0.00"0.0%
Sidewall height7.40"7.86"+0.46"+6.3%
Circumference96.77"99.68"+2.91"+3.0%
Revolutions per mile654.7635.6−19.1−2.9%

Speedometer difference

If your vehicle came with 235/80R16 and you fit 235/85R16, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.5 mph+1.5 mph
60 mph61.8 mph+1.8 mph
65 mph67.0 mph+2.0 mph
70 mph72.1 mph+2.1 mph
75 mph77.3 mph+2.3 mph
80 mph82.4 mph+2.4 mph

Each size on its own

Questions

Which is bigger, 235/80R16 or 235/85R16?
235/85R16 is taller by 0.93 inches (31.73" vs 30.80"). 235/80R16 is the same width.
Can I replace 235/80R16 with 235/85R16?
It is not recommended without checking carefully. The diameter difference is +3.0%, 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 235/85R16 change my speedometer?
When your speedometer reads 60 mph with 235/85R16 fitted (calibrated for 235/80R16), your real speed is 61.8 mph. Your odometer will under-count miles by about 3.0%.
Will 235/85R16 lift my vehicle?
Ride height changes by half the diameter difference: +0.46 inches of ground clearance at the axle.

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