255/55R20 vs 275/45R21 tire size
275/45R21 vs 255/55R20, diameter
-1.0% shorter
- Speedometer
- 60.6 mph
- At a true 60 mph
- Diameter
- 30.74 in
- Was 31.04 in
- Revs per mile
- 656
- Was 650
- 3% guideline
- Within
Car built for 255/55R20, now on 275/45R21.
255/55R20 and 275/45R21
| Measure | 255/55R20 | 275/45R21 | Difference |
|---|---|---|---|
| Width, mm | 255 | 275 | +20 |
| Sidewall, % of width | 55 | 45 | -10 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 5.52 | 4.87 | -0.65 |
| Diameter, in | 31.04 | 30.74 | -0.30 (-1.0%) |
| Circumference, in | 97.5 | 96.6 | -0.9 |
| Revs per mile | 650 | 656 | +6 (+1.0%) |
Fitting 275/45R21 instead of 255/55R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
- 20 mm wider. Check rubbing at full lock.
- Shorter sidewall: 0.6 in less.
Cars with 255/55R20
Cars with 275/45R21
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