305/30R19 vs 265/40R19
265/40R19 is outside the ±3% rule as a replacement for 305/30R19: the diameter differs by +4.36%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 265/40R19 on a car calibrated for 305/30R19, the speedometer reads 57.5 mph when you're really doing 60, and the odometer under-counts by 4.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.3 mph |
| 45 mph | 47.0 mph |
| 60 mph | 62.6 mph |
| 70 mph | 73.0 mph |
| 80 mph | 83.5 mph |
Other sizes close to 305/30R19
- 305/30R19 vs 225/45R18-0.89%
- 305/30R19 vs 235/45R18+0.47%
- 305/30R19 vs 245/40R19+1.95%
- 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%
Questions
Can I replace 305/30R19 with 265/40R19?
265/40R19 is outside the ±3% rule as a replacement for 305/30R19: the diameter differs by +4.36%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 305/30R19 and 265/40R19?
265/40R19 is 1.14" taller and 40 mm narrower; the sidewall is +0.57". At an indicated 60 mph you'd actually be doing 62.6 mph.
Will 265/40R19 fit on 305/30R19 wheels?
Both use a 19" rim, so the wheel diameter matches; check the wheel's width range for a 265 mm tire and the fender clearance.