345/30R19 vs 305/30R20
305/30R20 is a safe swap for 345/30R19 by the usual ±3% rule: the diameter differs by +0.20%.
Speedometer and odometer
With 305/30R20 on a car calibrated for 345/30R19, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.1 mph |
| 70 mph | 70.1 mph |
| 80 mph | 80.2 mph |
Other sizes close to 345/30R19
- 345/30R19 vs 235/50R18+0.38%
- 345/30R19 vs 245/45R19+1.96%
- 345/30R19 vs 245/40R19-1.60%
- 345/30R19 vs 235/40R19-2.76%
- 345/30R19 vs 255/40R19-0.44%
- 345/30R19 vs 255/35R19-4.13%
- 345/30R19 vs 255/45R19+3.26%
- 345/30R19 vs 275/35R19-2.10%
- 345/30R19 vs 275/40R19+1.89%
- 345/30R19 vs 255/35R20-0.45%
- 345/30R19 vs 225/40R19-3.92%
- 345/30R19 vs 225/45R19-0.65%
Questions
Can I replace 345/30R19 with 305/30R20?
305/30R20 is a safe swap for 345/30R19 by the usual ±3% rule: the diameter differs by +0.20%.
What's the difference between 345/30R19 and 305/30R20?
305/30R20 is 0.06" taller and 40 mm narrower; the sidewall is -0.47". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 305/30R20 fit on 345/30R19 wheels?
No — 345/30R19 needs a 19" wheel and 305/30R20 a 20" wheel. This is a plus/minus-size swap that changes wheels too.