265/45R20 vs 305/40R20
305/40R20 is a safe swap for 265/45R20 by the usual ±3% rule: the diameter differs by +0.74%.
Speedometer and odometer
With 305/40R20 on a car calibrated for 265/45R20, the speedometer reads 59.6 mph when you're really doing 60, and the odometer under-counts by 0.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.3 mph |
| 60 mph | 60.4 mph |
| 70 mph | 70.5 mph |
| 80 mph | 80.6 mph |
Other sizes close to 265/45R20
- 265/45R20 vs 235/55R19-0.72%
- 265/45R20 vs 245/45R20-2.41%
- 265/45R20 vs 255/45R20-1.21%
- 265/45R20 vs 255/50R20+2.21%
- 265/45R20 vs 275/40R20-2.48%
- 265/45R20 vs 265/50R20+3.55%
- 265/45R20 vs 245/50R20+0.87%
- 265/45R20 vs 275/45R20+1.21%
- 265/45R20 vs 235/55R20+2.68%
- 265/45R20 vs 255/40R20-4.62%
- 265/45R20 vs 245/55R19+0.75%
- 265/45R20 vs 265/50R19+0.15%
Questions
Can I replace 265/45R20 with 305/40R20?
305/40R20 is a safe swap for 265/45R20 by the usual ±3% rule: the diameter differs by +0.74%.
What's the difference between 265/45R20 and 305/40R20?
305/40R20 is 0.22" taller and 40 mm wider; the sidewall is +0.11". At an indicated 60 mph you'd actually be doing 60.4 mph.
Will 305/40R20 fit on 265/45R20 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.