305/25R20 vs 305/30R19
305/30R19 is a safe swap for 305/25R20 by the usual ±3% rule: the diameter differs by +0.77%.
Speedometer and odometer
With 305/30R19 on a car calibrated for 305/25R20, the speedometer reads 59.5 mph when you're really doing 60, and the odometer under-counts by 0.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.3 mph |
| 60 mph | 60.5 mph |
| 70 mph | 70.5 mph |
| 80 mph | 80.6 mph |
Other sizes close to 305/25R20
- 305/25R20 vs 255/35R19+0.09%
- 305/25R20 vs 245/35R20+2.88%
- 305/25R20 vs 255/35R20+3.94%
- 305/25R20 vs 245/35R19-0.97%
- 305/25R20 vs 225/40R19+0.32%
- 305/25R20 vs 285/30R20+2.80%
- 305/25R20 vs 275/30R20+1.89%
- 305/25R20 vs 265/35R20+5.00%
- 305/25R20 vs 235/35R20+1.82%
- 305/25R20 vs 295/30R20+3.71%
- 305/25R20 vs 305/30R20+4.62%
- 305/25R20 vs 295/30R19-0.14%
Questions
Can I replace 305/25R20 with 305/30R19?
305/30R19 is a safe swap for 305/25R20 by the usual ±3% rule: the diameter differs by +0.77%.
What's the difference between 305/25R20 and 305/30R19?
305/30R19 is 0.20" taller and 0 mm wider; the sidewall is +0.60". At an indicated 60 mph you'd actually be doing 60.5 mph.
Will 305/30R19 fit on 305/25R20 wheels?
No — 305/25R20 needs a 20" wheel and 305/30R19 a 19" wheel. This is a plus/minus-size swap that changes wheels too.