265/30R20 vs 305/30R20
305/30R20 is outside the ±3% rule as a replacement for 265/30R20: the diameter differs by +3.60%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 305/30R20 on a car calibrated for 265/30R20, the speedometer reads 57.9 mph when you're really doing 60, and the odometer under-counts by 3.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.1 mph |
| 45 mph | 46.6 mph |
| 60 mph | 62.2 mph |
| 70 mph | 72.5 mph |
| 80 mph | 82.9 mph |
Other sizes close to 265/30R20
- 265/30R20 vs 235/40R19+0.54%
- 265/30R20 vs 255/35R19-0.88%
- 265/30R20 vs 245/35R20+1.87%
- 265/30R20 vs 255/35R20+2.92%
- 265/30R20 vs 225/40R19-0.66%
- 265/30R20 vs 265/35R19+0.16%
- 265/30R20 vs 285/30R20+1.80%
- 265/30R20 vs 275/30R20+0.90%
- 265/30R20 vs 265/35R20+3.97%
- 265/30R20 vs 235/35R20+0.82%
- 265/30R20 vs 295/30R20+2.70%
- 265/30R20 vs 305/30R19-0.21%
Questions
Can I replace 265/30R20 with 305/30R20?
305/30R20 is outside the ±3% rule as a replacement for 265/30R20: the diameter differs by +3.60%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 265/30R20 and 305/30R20?
305/30R20 is 0.94" taller and 40 mm wider; the sidewall is +0.47". At an indicated 60 mph you'd actually be doing 62.2 mph.
Will 305/30R20 fit on 265/30R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.