305/30R19 vs 245/40R19
245/40R19 is a safe swap for 305/30R19 by the usual ±3% rule: the diameter differs by +1.95%.
Speedometer and odometer
With 245/40R19 on a car calibrated for 305/30R19, the speedometer reads 58.9 mph when you're really doing 60, and the odometer under-counts by 2.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.6 mph |
| 45 mph | 45.9 mph |
| 60 mph | 61.2 mph |
| 70 mph | 71.4 mph |
| 80 mph | 81.6 mph |
Other sizes close to 305/30R19
- 305/30R19 vs 225/45R18-0.89%
- 305/30R19 vs 235/45R18+0.47%
- 305/30R19 vs 235/40R19+0.75%
- 305/30R19 vs 255/40R19+3.16%
- 305/30R19 vs 255/35R19-0.68%
- 305/30R19 vs 255/40R18-0.66%
- 305/30R19 vs 275/35R19+1.43%
- 305/30R19 vs 245/35R19-1.73%
- 305/30R19 vs 225/40R19-0.45%
- 305/30R19 vs 235/35R19-2.78%
- 305/30R19 vs 225/45R19+2.93%
- 305/30R19 vs 285/35R19+2.48%
Questions
Can I replace 305/30R19 with 245/40R19?
245/40R19 is a safe swap for 305/30R19 by the usual ±3% rule: the diameter differs by +1.95%.
What's the difference between 305/30R19 and 245/40R19?
245/40R19 is 0.51" taller and 60 mm narrower; the sidewall is +0.26". At an indicated 60 mph you'd actually be doing 61.2 mph.
Will 245/40R19 fit on 305/30R19 wheels?
Both use a 19" rim, so the wheel diameter matches; check the wheel's width range for a 245 mm tire and the fender clearance.