Tire Size Box

225/75R15 vs 225/85R15

225/85R15 compared with 225/75R15

+6.3% diameter, 0.0" width

225/85R15 is 30.06" tall vs 28.29". More than the 3% rule of thumb, so check carefully before switching.

28.3"15" rim6.6"8.9" wide
225/75R15 (solid) compared with 225/85R15 (dashed outline), drawn to scale

With 225/85R15 tires, when your speedometer says 60 mph you are really going

63.8 mph

225/85R15 is +1.77 inches (+6.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/75R15225/85R15Difference%
Overall diameter28.29"30.06"+1.77"+6.3%
Section width8.86"8.86"0.00"0.0%
Sidewall height6.64"7.53"+0.89"+13.3%
Circumference88.87"94.43"+5.57"+6.3%
Revolutions per mile713.0670.9−42.0−5.9%

Speedometer difference

If your vehicle came with 225/75R15 and you fit 225/85R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.3 mph+1.3 mph
30 mph31.9 mph+1.9 mph
40 mph42.5 mph+2.5 mph
50 mph53.1 mph+3.1 mph
60 mph63.8 mph+3.8 mph
65 mph69.1 mph+4.1 mph
70 mph74.4 mph+4.4 mph
75 mph79.7 mph+4.7 mph
80 mph85.0 mph+5.0 mph

Each size on its own

Questions

Which is bigger, 225/75R15 or 225/85R15?
225/85R15 is taller by 1.77 inches (30.06" vs 28.29"). 225/75R15 is the same width.
Can I replace 225/75R15 with 225/85R15?
It is not recommended without checking carefully. The diameter difference is +6.3%, 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 225/85R15 change my speedometer?
When your speedometer reads 60 mph with 225/85R15 fitted (calibrated for 225/75R15), your real speed is 63.8 mph. Your odometer will under-count miles by about 6.3%.
Will 225/85R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.89 inches of ground clearance at the axle.

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