285/35R20 vs 255/35R21 tire size
255/35R21 vs 285/35R20, diameter
+0.6% taller
- Speedometer
- 59.6 mph
- At a true 60 mph
- Diameter
- 28.03 in
- Was 27.85 in
- Revs per mile
- 720
- Was 724
- 3% guideline
- Within
Car built for 285/35R20, now on 255/35R21.
285/35R20 and 255/35R21
| Measure | 285/35R20 | 255/35R21 | Difference |
|---|---|---|---|
| Width, mm | 285 | 255 | -30 |
| Sidewall, % of width | 35 | 35 | 0 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 3.93 | 3.51 | -0.41 |
| Diameter, in | 27.85 | 28.03 | +0.17 (+0.6%) |
| Circumference, in | 87.5 | 88.1 | +0.5 |
| Revs per mile | 724 | 720 | -4 (-0.6%) |
Fitting 255/35R21 instead of 285/35R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
Cars with 255/35R21
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