255/45R20 vs 285/40R20 tire size
285/40R20 vs 255/45R20, diameter
-0.2% shorter
- Speedometer
- 60.1 mph
- At a true 60 mph
- Diameter
- 28.98 in
- Was 29.04 in
- Revs per mile
- 696
- Was 695
- 3% guideline
- Within
Car built for 255/45R20, now on 285/40R20.
255/45R20 and 285/40R20
| Measure | 255/45R20 | 285/40R20 | Difference |
|---|---|---|---|
| Width, mm | 255 | 285 | +30 |
| Sidewall, % of width | 45 | 40 | -5 |
| Rim, in | 20 | 20 | 0 |
| Section height, in | 4.52 | 4.49 | -0.03 |
| Diameter, in | 29.04 | 28.98 | -0.06 (-0.2%) |
| Circumference, in | 91.2 | 91.0 | -0.2 |
| Revs per mile | 695 | 696 | +1 (+0.2%) |
Fitting 285/40R20 instead of 255/45R20
Within the usual 3% diameter guideline.
- 30 mm wider. Check rubbing at full lock.
Cars with 255/45R20
Cars with 285/40R20
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