275/45R20 vs 245/45R21 tire size
245/45R21 vs 275/45R20, diameter
-0.2% shorter
- Speedometer
- 60.1 mph
- At a true 60 mph
- Diameter
- 29.68 in
- Was 29.74 in
- Revs per mile
- 679
- Was 678
- 3% guideline
- Within
Car built for 275/45R20, now on 245/45R21.
275/45R20 and 245/45R21
| Measure | 275/45R20 | 245/45R21 | Difference |
|---|---|---|---|
| Width, mm | 275 | 245 | -30 |
| Sidewall, % of width | 45 | 45 | 0 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 4.87 | 4.34 | -0.53 |
| Diameter, in | 29.74 | 29.68 | -0.06 (-0.2%) |
| Circumference, in | 93.4 | 93.2 | -0.2 |
| Revs per mile | 678 | 679 | +1 (+0.2%) |
Fitting 245/45R21 instead of 275/45R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
- Shorter sidewall: 0.5 in less.
Cars with 275/45R20
Cars with 245/45R21
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