305/50R20 vs 275/50R21 tire size
275/50R21 vs 305/50R20, diameter
-0.6% shorter
- Speedometer
- 60.3 mph
- At a true 60 mph
- Diameter
- 31.83 in
- Was 32.01 in
- Revs per mile
- 634
- Was 630
- 3% guideline
- Within
Car built for 305/50R20, now on 275/50R21.
305/50R20 and 275/50R21
| Measure | 305/50R20 | 275/50R21 | Difference |
|---|---|---|---|
| Width, mm | 305 | 275 | -30 |
| Sidewall, % of width | 50 | 50 | 0 |
| Rim, in | 20 | 21 | +1 |
| Section height, in | 6.00 | 5.41 | -0.59 |
| Diameter, in | 32.01 | 31.83 | -0.18 (-0.6%) |
| Circumference, in | 100.6 | 100.0 | -0.6 |
| Revs per mile | 630 | 634 | +4 (+0.6%) |
Fitting 275/50R21 instead of 305/50R20
Within the usual 3% diameter guideline.
- Needs 21 in wheels.
- Shorter sidewall: 0.6 in less.
Cars with 275/50R21
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