255/65R20 vs 275/55R21 tire size
275/55R21 vs 255/65R20, diameter
-0.4% shorter
- Speedometer
- 60.3 mph
- At a true 60 mph
- Diameter
- 32.91 in
- Was 33.05 in
- Revs per mile
- 613
- Was 610
- 3% guideline
- Within
Car built for 255/65R20, now on 275/55R21.
255/65R20 and 275/55R21
| Measure | 255/65R20 | 275/55R21 | Difference |
|---|---|---|---|
| Width, mm | 255 | 275 | +20 |
| Sidewall, % of width | 65 | 55 | -10 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 6.53 | 5.95 | -0.57 |
| Diameter, in | 33.05 | 32.91 | -0.14 (-0.4%) |
| Circumference, in | 103.8 | 103.4 | -0.4 |
| Revs per mile | 610 | 613 | +3 (+0.4%) |
Fitting 275/55R21 instead of 255/65R20
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 255/65R20
Cars with 275/55R21
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