255/40R19 vs 305/30R20 tire size
305/30R20 vs 255/40R19, diameter
+0.6% taller
- Speedometer
- 59.6 mph
- At a true 60 mph
- Diameter
- 27.20 in
- Was 27.03 in
- Revs per mile
- 741
- Was 746
- 3% guideline
- Within
Car built for 255/40R19, now on 305/30R20.
255/40R19 and 305/30R20
| Measure | 255/40R19 | 305/30R20 | Difference |
|---|---|---|---|
| Width, mm | 255 | 305 | +50 |
| Sidewall, % of width | 40 | 30 | -10 |
| Rim, in | 19 | 20 | +1 |
| Section height, in | 4.02 | 3.60 | -0.41 |
| Diameter, in | 27.03 | 27.20 | +0.17 (+0.6%) |
| Circumference, in | 84.9 | 85.5 | +0.5 |
| Revs per mile | 746 | 741 | -5 (-0.6%) |
Fitting 305/30R20 instead of 255/40R19
Within the usual 3% diameter guideline.
- Needs 20 in wheels.
- 50 mm wider. Check rubbing at full lock.
Cars with 255/40R19
Cars with 305/30R20
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