255/50R20 vs 235/50R21 tire size
235/50R21 vs 255/50R20, diameter
+0.7% taller
- Speedometer
- 59.6 mph
- At a true 60 mph
- Diameter
- 30.25 in
- Was 30.04 in
- Revs per mile
- 667
- Was 671
- 3% guideline
- Within
Car built for 255/50R20, now on 235/50R21.
255/50R20 and 235/50R21
| Measure | 255/50R20 | 235/50R21 | Difference |
|---|---|---|---|
| Width, mm | 255 | 235 | -20 |
| Sidewall, % of width | 50 | 50 | 0 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 5.02 | 4.63 | -0.39 |
| Diameter, in | 30.04 | 30.25 | +0.21 (+0.7%) |
| Circumference, in | 94.4 | 95.0 | +0.7 |
| Revs per mile | 671 | 667 | -5 (-0.7%) |
Fitting 235/50R21 instead of 255/50R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
Cars with 255/50R20
Cars with 235/50R21
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