285/70R17 vs 255/70R18 tire size
255/70R18 vs 285/70R17, diameter
-2.0% shorter
- Speedometer
- 61.2 mph
- At a true 60 mph
- Diameter
- 32.06 in
- Was 32.71 in
- Revs per mile
- 629
- Was 617
- 3% guideline
- Within
Car built for 285/70R17, now on 255/70R18.
285/70R17 and 255/70R18
| Measure | 285/70R17 | 255/70R18 | Difference |
|---|---|---|---|
| Width, mm | 285 | 255 | -30 |
| Sidewall, % of width | 70 | 70 | 0 |
| Rim, in | 17 | 18 | +1 |
| Section height, in | 7.85 | 7.03 | -0.83 |
| Diameter, in | 32.71 | 32.06 | -0.65 (-2.0%) |
| Circumference, in | 102.8 | 100.7 | -2.1 |
| Revs per mile | 617 | 629 | +13 (+2.0%) |
Fitting 255/70R18 instead of 285/70R17
Within the usual 3% diameter guideline.
- Needs 18 in wheels.
- Shorter sidewall: 0.8 in less.
Cars with 285/70R17
Cars with 255/70R18
What this cannot tell you
Diameter within 3% is a common shop guideline, not a maker spec.
Load index, offset and clearance are not in this data.
- Two or more sources agree
- One source
- Model-level or estimate
- Sources differ