235/45R20 vs 255/35R21 tire size
255/35R21 vs 235/45R20, diameter
-1.1% shorter
- Speedometer
- 60.6 mph
- At a true 60 mph
- Diameter
- 28.03 in
- Was 28.33 in
- Revs per mile
- 720
- Was 712
- 3% guideline
- Within
Car built for 235/45R20, now on 255/35R21.
235/45R20 and 255/35R21
| Measure | 235/45R20 | 255/35R21 | Difference |
|---|---|---|---|
| Width, mm | 235 | 255 | +20 |
| Sidewall, % of width | 45 | 35 | -10 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 4.16 | 3.51 | -0.65 |
| Diameter, in | 28.33 | 28.03 | -0.30 (-1.1%) |
| Circumference, in | 89.0 | 88.1 | -0.9 |
| Revs per mile | 712 | 720 | +8 (+1.1%) |
Fitting 255/35R21 instead of 235/45R20
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 235/45R20
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