245/45R20 vs 245/40R21 tire size
245/40R21 vs 245/45R20, diameter
+0.1% taller
- Speedometer
- 59.9 mph
- At a true 60 mph
- Diameter
- 28.72 in
- Was 28.68 in
- Revs per mile
- 702
- Was 703
- 3% guideline
- Within
Car built for 245/45R20, now on 245/40R21.
245/45R20 and 245/40R21
| Measure | 245/45R20 | 245/40R21 | Difference |
|---|---|---|---|
| Width, mm | 245 | 245 | 0 |
| Sidewall, % of width | 45 | 40 | -5 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 4.34 | 3.86 | -0.48 |
| Diameter, in | 28.68 | 28.72 | +0.04 (+0.1%) |
| Circumference, in | 90.1 | 90.2 | +0.1 |
| Revs per mile | 703 | 702 | -1 (-0.1%) |
Fitting 245/40R21 instead of 245/45R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
Cars with 245/45R20
Cars with 245/40R21
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