235/55R17 vs 255/45R18 tire size
255/45R18 vs 235/55R17, diameter
-0.5% shorter
- Speedometer
- 60.3 mph
- At a true 60 mph
- Diameter
- 27.04 in
- Was 27.18 in
- Revs per mile
- 746
- Was 742
- 3% guideline
- Within
Car built for 235/55R17, now on 255/45R18.
235/55R17 and 255/45R18
| Measure | 235/55R17 | 255/45R18 | Difference |
|---|---|---|---|
| Width, mm | 235 | 255 | +20 |
| Sidewall, % of width | 55 | 45 | -10 |
| Rim, in | 17 | 18 | +1 |
| Section height, in | 5.09 | 4.52 | -0.57 |
| Diameter, in | 27.18 | 27.04 | -0.14 (-0.5%) |
| Circumference, in | 85.4 | 84.9 | -0.4 |
| Revs per mile | 742 | 746 | +4 (+0.5%) |
Fitting 255/45R18 instead of 235/55R17
Within the usual 3% diameter guideline.
- Needs 18 in wheels.
- 20 mm wider. Check rubbing at full lock.
- Shorter sidewall: 0.6 in less.
Cars with 255/45R18
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