255/50R17 vs 235/50R18 tire size
235/50R18 vs 255/50R17, diameter
+0.8% taller
- Speedometer
- 59.5 mph
- At a true 60 mph
- Diameter
- 27.25 in
- Was 27.04 in
- Revs per mile
- 740
- Was 746
- 3% guideline
- Within
Car built for 255/50R17, now on 235/50R18.
255/50R17 and 235/50R18
| Measure | 255/50R17 | 235/50R18 | Difference |
|---|---|---|---|
| Width, mm | 255 | 235 | -20 |
| Sidewall, % of width | 50 | 50 | 0 |
| Rim, in | 17 | 18 | +1 |
| Section height, in | 5.02 | 4.63 | -0.39 |
| Diameter, in | 27.04 | 27.25 | +0.21 (+0.8%) |
| Circumference, in | 84.9 | 85.6 | +0.7 |
| Revs per mile | 746 | 740 | -6 (-0.8%) |
Fitting 235/50R18 instead of 255/50R17
Within the usual 3% diameter guideline.
- Needs 18 in wheels.
Cars with 255/50R17
Cars with 235/50R18
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