235/55R18 vs 315/40R18 tire size
315/40R18 vs 235/55R18, diameter
-0.9% shorter
- Speedometer
- 60.5 mph
- At a true 60 mph
- Diameter
- 27.92 in
- Was 28.18 in
- Revs per mile
- 722
- Was 716
- 3% guideline
- Within
Car built for 235/55R18, now on 315/40R18.
235/55R18 and 315/40R18
| Measure | 235/55R18 | 315/40R18 | Difference |
|---|---|---|---|
| Width, mm | 235 | 315 | +80 |
| Sidewall, % of width | 55 | 40 | -15 |
| Rim, in | 18 | 18 | 0 |
| Section height, in | 5.09 | 4.96 | -0.13 |
| Diameter, in | 28.18 | 27.92 | -0.26 (-0.9%) |
| Circumference, in | 88.5 | 87.7 | -0.8 |
| Revs per mile | 716 | 722 | +7 (+0.9%) |
Fitting 315/40R18 instead of 235/55R18
Within the usual 3% diameter guideline.
- 80 mm wider. Check rubbing at full lock.
Cars with 235/55R18
Cars with 315/40R18
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