255/75R17 vs 285/70R17 — two factory Wrangler sizes
Sahara against Rubicon, measured. What a used buyer is comparing when two examples wear different tires.
285/70R17 is 0.65 in taller than 255/75R17 (2.03%) and 1.18 in wider. A speedometer calibrated for 255/75R17 would under-read by 2.03%.
Measured against each other
Overall diameter
32.06 in32.71 in+0.65 in (+2.03%)Section width
10.04 in / 255 mm11.22 in / 285 mm+1.18 in (+11.76%)Sidewall height
7.53 in7.85 in+0.32 inCircumference
100.7 in102.8 in+2.0 inRevolutions per mile
629.1616.6-12.5Ride height at the axle
——+0.32 inSpeedometer reading
——+2.03% under-read
| Dimension | 255/75R17 | 285/70R17 | Change |
|---|---|---|---|
| Overall diameter | 32.06 in | 32.71 in | +0.65 in (+2.03%) |
| Section width | 10.04 in / 255 mm | 11.22 in / 285 mm | +1.18 in (+11.76%) |
| Sidewall height | 7.53 in | 7.85 in | +0.32 in |
| Circumference | 100.7 in | 102.8 in | +2.0 in |
| Revolutions per mile | 629.1 | 616.6 | -12.5 |
| Ride height at the axle | — | — | +0.32 in |
| Speedometer reading | — | — | +2.03% under-read |
Calibrated for 255/75R17, running 285/70R17
- Dial reads 30
- 30.6 mph
- Dial reads 50
- 51.0 mph
- Dial reads 70
- 71.4 mph
- Odometer counts 100
- 102.0 mi covered
Change either size in the comparison tool, or see the full speed table in the speedometer error calculator.
Both of these left the factory on the same model in the same years. The comparison is not an upgrade path; it is what distinguishes two trims when you look underneath them.
Close on height, further apart on width
- Diameter: 32.06 in and 32.71 in — 0.65 in apart, 2.03%
- Section width: 10.04 in and 11.22 in — 1.18 in apart, 11.76%
The width gap is nearly twice the height gap in inches and roughly six times as large proportionally. Two trims that look meaningfully different from the front are barely different in how far off the ground they sit.
Where the height difference comes from
Not from the aspect ratio, which drops from 75 to 70 and works against the change. It comes entirely from the 30 mm of extra width, which adds enough sidewall at 70% to overcome the profile reduction and leave 0.65 in over.
Sidewall: 7.53 in on the narrower size, 7.85 in on the wider one. A third of an inch, for 30 mm of casing.
What a used buyer should take from it
Essentially nothing about the vehicle's gearing or instrumentation, since 2.03% is inside the range tire wear alone will produce. The needle is light by four-tenths of a mile an hour at 20, and by 1.4 mph at 70.
What differs is stance, tread availability and replacement cost. The wider size is offered in more aggressive patterns and is the more expensive of the two to replace in most families.
The narrow size's advantage
A 10.04 in casing turns inside tighter spaces than an 11.22 in one, and on a short-wheelbase four-wheel-drive the steering stop is frequently the binding constraint. The 1.18 in between those two nominal figures is the whole of what this page can put a number on. How much of it survives on a given truck depends on the wheels: a casing fitted narrower than the rim width it was specified against draws its shoulders in and measures under its nominal figure, and neither that specification nor the width of anybody's wheels is recorded here.
The count, and what it is worth
629.1 revolutions per mile against 616.6 — a dozen rotations apart. Put against the 245/75R17 the Sport trim wears, at 640.9, the three factory sizes span roughly twenty-four revolutions per mile in total. The whole factory range is narrower than a single aftermarket step.
Going further from either
From the narrower start, the common destinations are a 33 or a 35. From the wider one, the step is straight to a 35 — the two trims converge on the same tire from different directions.