285/40R20 vs 285/35R21 tire size
285/35R21 vs 285/40R20, diameter
-0.4% shorter
- Speedometer
- 60.3 mph
- At a true 60 mph
- Diameter
- 28.85 in
- Was 28.98 in
- Revs per mile
- 699
- Was 696
- 3% guideline
- Within
Car built for 285/40R20, now on 285/35R21.
285/40R20 and 285/35R21
| Measure | 285/40R20 | 285/35R21 | Difference |
|---|---|---|---|
| Width, mm | 285 | 285 | 0 |
| Sidewall, % of width | 40 | 35 | -5 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 4.49 | 3.93 | -0.56 |
| Diameter, in | 28.98 | 28.85 | -0.12 (-0.4%) |
| Circumference, in | 91.0 | 90.6 | -0.4 |
| Revs per mile | 696 | 699 | +3 (+0.4%) |
Fitting 285/35R21 instead of 285/40R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
- Shorter sidewall: 0.6 in less.
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