315/70R17 vs 305/70R18 tire size
305/70R18 vs 315/70R17, diameter
+1.3% taller
- Speedometer
- 59.2 mph
- At a true 60 mph
- Diameter
- 34.81 in
- Was 34.36 in
- Revs per mile
- 579
- Was 587
- 3% guideline
- Within
Car built for 315/70R17, now on 305/70R18.
315/70R17 and 305/70R18
| Measure | 315/70R17 | 305/70R18 | Difference |
|---|---|---|---|
| Width, mm | 315 | 305 | -10 |
| Sidewall, % of width | 70 | 70 | 0 |
| Rim, in | 17 | 18 | +1 |
| Section height, in | 8.68 | 8.41 | -0.28 |
| Diameter, in | 34.36 | 34.81 | +0.45 (+1.3%) |
| Circumference, in | 108.0 | 109.4 | +1.4 |
| Revs per mile | 587 | 579 | -8 (-1.3%) |
Fitting 305/70R18 instead of 315/70R17
Within the usual 3% diameter guideline.
- Needs 18 in wheels.
Cars with 315/70R17
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