245/45R20 vs 285/35R21 tire size
285/35R21 vs 245/45R20, diameter
+0.6% taller
- Speedometer
- 59.6 mph
- At a true 60 mph
- Diameter
- 28.85 in
- Was 28.68 in
- Revs per mile
- 699
- Was 703
- 3% guideline
- Within
Car built for 245/45R20, now on 285/35R21.
245/45R20 and 285/35R21
| Measure | 245/45R20 | 285/35R21 | Difference |
|---|---|---|---|
| Width, mm | 245 | 285 | +40 |
| Sidewall, % of width | 45 | 35 | -10 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 4.34 | 3.93 | -0.41 |
| Diameter, in | 28.68 | 28.85 | +0.17 (+0.6%) |
| Circumference, in | 90.1 | 90.6 | +0.5 |
| Revs per mile | 703 | 699 | -4 (-0.6%) |
Fitting 285/35R21 instead of 245/45R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
- 40 mm wider. Check rubbing at full lock.
Cars with 245/45R20
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