275/45R20 vs 275/40R21 tire size
275/40R21 vs 275/45R20, diameter
-0.3% shorter
- Speedometer
- 60.2 mph
- At a true 60 mph
- Diameter
- 29.66 in
- Was 29.74 in
- Revs per mile
- 680
- Was 678
- 3% guideline
- Within
Car built for 275/45R20, now on 275/40R21.
275/45R20 and 275/40R21
| Measure | 275/45R20 | 275/40R21 | Difference |
|---|---|---|---|
| Width, mm | 275 | 275 | 0 |
| Sidewall, % of width | 45 | 40 | -5 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 4.87 | 4.33 | -0.54 |
| Diameter, in | 29.74 | 29.66 | -0.08 (-0.3%) |
| Circumference, in | 93.4 | 93.2 | -0.3 |
| Revs per mile | 678 | 680 | +2 (+0.3%) |
Fitting 275/40R21 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 275/40R21
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