245/45R21 vs 285/40R21 tire size
285/40R21 vs 245/45R21, diameter
+1.0% taller
- Speedometer
- 59.4 mph
- At a true 60 mph
- Diameter
- 29.98 in
- Was 29.68 in
- Revs per mile
- 673
- Was 679
- 3% guideline
- Within
Car built for 245/45R21, now on 285/40R21.
245/45R21 and 285/40R21
| Measure | 245/45R21 | 285/40R21 | Difference |
|---|---|---|---|
| Width, mm | 245 | 285 | +40 |
| Sidewall, % of width | 45 | 40 | -5 |
| Rim, in | 21 | 21 | 0 |
| Section height, in | 4.34 | 4.49 | +0.15 |
| Diameter, in | 29.68 | 29.98 | +0.30 (+1.0%) |
| Circumference, in | 93.2 | 94.2 | +0.9 |
| Revs per mile | 679 | 673 | -7 (-1.0%) |
Fitting 285/40R21 instead of 245/45R21
Within the usual 3% diameter guideline.
- 40 mm wider. Check rubbing at full lock.
Cars with 245/45R21
Cars with 285/40R21
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