Tire Size Box

235/75R13 vs 235/85R13

235/85R13 compared with 235/75R13

+6.9% diameter, 0.0" width

235/85R13 is 28.73" tall vs 26.88". More than the 3% rule of thumb, so check carefully before switching.

26.9"13" rim6.9"9.3" wide
235/75R13 (solid) compared with 235/85R13 (dashed outline), drawn to scale

With 235/85R13 tires, when your speedometer says 60 mph you are really going

64.1 mph

235/85R13 is +1.85 inches (+6.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/75R13235/85R13Difference%
Overall diameter26.88"28.73"+1.85"+6.9%
Section width9.25"9.25"0.00"0.0%
Sidewall height6.94"7.86"+0.93"+13.3%
Circumference84.44"90.25"+5.81"+6.9%
Revolutions per mile750.4702.0−48.3−6.4%

Speedometer difference

If your vehicle came with 235/75R13 and you fit 235/85R13, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.1 mph+2.1 mph
40 mph42.8 mph+2.8 mph
50 mph53.4 mph+3.4 mph
60 mph64.1 mph+4.1 mph
65 mph69.5 mph+4.5 mph
70 mph74.8 mph+4.8 mph
75 mph80.2 mph+5.2 mph
80 mph85.5 mph+5.5 mph

Each size on its own

Questions

Which is bigger, 235/75R13 or 235/85R13?
235/85R13 is taller by 1.85 inches (28.73" vs 26.88"). 235/75R13 is the same width.
Can I replace 235/75R13 with 235/85R13?
It is not recommended without checking carefully. The diameter difference is +6.9%, 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 235/85R13 change my speedometer?
When your speedometer reads 60 mph with 235/85R13 fitted (calibrated for 235/75R13), your real speed is 64.1 mph. Your odometer will under-count miles by about 6.9%.
Will 235/85R13 lift my vehicle?
Ride height changes by half the diameter difference: +0.93 inches of ground clearance at the axle.

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