285/75R17 vs 305/70R18 tire size
305/70R18 vs 285/75R17, diameter
+2.9% taller
- Speedometer
- 58.3 mph
- At a true 60 mph
- Diameter
- 34.81 in
- Was 33.83 in
- Revs per mile
- 579
- Was 596
- 3% guideline
- Within
Car built for 285/75R17, now on 305/70R18.
285/75R17 and 305/70R18
| Measure | 285/75R17 | 305/70R18 | Difference |
|---|---|---|---|
| Width, mm | 285 | 305 | +20 |
| Sidewall, % of width | 75 | 70 | -5 |
| Rim, in | 17 | 18 | +1 |
| Section height, in | 8.42 | 8.41 | -0.01 |
| Diameter, in | 33.83 | 34.81 | +0.98 (+2.9%) |
| Circumference, in | 106.3 | 109.4 | +3.1 |
| Revs per mile | 596 | 579 | -17 (-2.8%) |
Fitting 305/70R18 instead of 285/75R17
Within the usual 3% diameter guideline.
- Needs 18 in wheels.
- 20 mm wider. Check rubbing at full lock.
Cars with 285/75R17
Cars with 305/70R18
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