225/45R18 vs 255/40R18 tire size
255/40R18 vs 225/45R18, diameter
+0.2% taller
- Speedometer
- 59.9 mph
- At a true 60 mph
- Diameter
- 26.03 in
- Was 25.97 in
- Revs per mile
- 775
- Was 777
- 3% guideline
- Within
Car built for 225/45R18, now on 255/40R18.
225/45R18 and 255/40R18
| Measure | 225/45R18 | 255/40R18 | Difference |
|---|---|---|---|
| Width, mm | 225 | 255 | +30 |
| Sidewall, % of width | 45 | 40 | -5 |
| Rim, in | 18 | 18 | 0 |
| Section height, in | 3.99 | 4.02 | +0.03 |
| Diameter, in | 25.97 | 26.03 | +0.06 (+0.2%) |
| Circumference, in | 81.6 | 81.8 | +0.2 |
| Revs per mile | 777 | 775 | -2 (-0.2%) |
Fitting 255/40R18 instead of 225/45R18
Within the usual 3% diameter guideline.
- 30 mm wider. Check rubbing at full lock.
Cars with 225/45R18
Cars with 255/40R18
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