275/45R20 vs 255/45R21 tire size
255/45R21 vs 275/45R20, diameter
+1.0% taller
- Speedometer
- 59.4 mph
- At a true 60 mph
- Diameter
- 30.04 in
- Was 29.74 in
- Revs per mile
- 671
- Was 678
- 3% guideline
- Within
Car built for 275/45R20, now on 255/45R21.
275/45R20 and 255/45R21
| Measure | 275/45R20 | 255/45R21 | Difference |
|---|---|---|---|
| Width, mm | 275 | 255 | -20 |
| Sidewall, % of width | 45 | 45 | 0 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 4.87 | 4.52 | -0.35 |
| Diameter, in | 29.74 | 30.04 | +0.29 (+1.0%) |
| Circumference, in | 93.4 | 94.4 | +0.9 |
| Revs per mile | 678 | 671 | -7 (-1.0%) |
Fitting 255/45R21 instead of 275/45R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
Cars with 275/45R20
Cars with 255/45R21
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