205/55R17 vs 245/40R18 tire size
245/40R18 vs 205/55R17, diameter
-0.6% shorter
- Speedometer
- 60.4 mph
- At a true 60 mph
- Diameter
- 25.72 in
- Was 25.88 in
- Revs per mile
- 784
- Was 779
- 3% guideline
- Within
Car built for 205/55R17, now on 245/40R18.
205/55R17 and 245/40R18
| Measure | 205/55R17 | 245/40R18 | Difference |
|---|---|---|---|
| Width, mm | 205 | 245 | +40 |
| Sidewall, % of width | 55 | 40 | -15 |
| Rim, in | 17 | 18 | +1 |
| Section height, in | 4.44 | 3.86 | -0.58 |
| Diameter, in | 25.88 | 25.72 | -0.16 (-0.6%) |
| Circumference, in | 81.3 | 80.8 | -0.5 |
| Revs per mile | 779 | 784 | +5 (+0.6%) |
Fitting 245/40R18 instead of 205/55R17
Within the usual 3% diameter guideline.
- Needs 18 in wheels.
- 40 mm wider. Check rubbing at full lock.
- Shorter sidewall: 0.6 in less.
Cars with 205/55R17
Cars with 245/40R18
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