285/50R20 vs 255/50R21 tire size
255/50R21 vs 285/50R20, diameter
-0.6% shorter
- Speedometer
- 60.4 mph
- At a true 60 mph
- Diameter
- 31.04 in
- Was 31.22 in
- Revs per mile
- 650
- Was 646
- 3% guideline
- Within
Car built for 285/50R20, now on 255/50R21.
285/50R20 and 255/50R21
| Measure | 285/50R20 | 255/50R21 | Difference |
|---|---|---|---|
| Width, mm | 285 | 255 | -30 |
| Sidewall, % of width | 50 | 50 | 0 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 5.61 | 5.02 | -0.59 |
| Diameter, in | 31.22 | 31.04 | -0.18 (-0.6%) |
| Circumference, in | 98.1 | 97.5 | -0.6 |
| Revs per mile | 646 | 650 | +4 (+0.6%) |
Fitting 255/50R21 instead of 285/50R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
- Shorter sidewall: 0.6 in less.
Cars with 285/50R20
Cars with 255/50R21
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