265/40R21 vs 265/45R20
265/45R20 is a safe swap for 265/40R21 by the usual ±3% rule: the diameter differs by +0.15%.
Speedometer and odometer
With 265/45R20 on a car calibrated for 265/40R21, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.0 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.1 mph |
| 70 mph | 70.1 mph |
| 80 mph | 80.1 mph |
Other sizes close to 265/40R21
- 265/40R21 vs 275/35R21-2.62%
- 265/40R21 vs 295/35R21-0.74%
- 265/40R21 vs 275/45R21+4.76%
- 265/40R21 vs 255/40R21-1.07%
- 265/40R21 vs 265/35R21-3.56%
- 265/40R21 vs 265/35R22-0.15%
- 265/40R21 vs 295/40R20-0.19%
- 265/40R21 vs 295/40R21+3.22%
- 265/40R21 vs 285/40R21+2.15%
- 265/40R21 vs 265/45R21+3.56%
- 265/40R21 vs 325/30R21-2.28%
- 265/40R21 vs 235/50R20-0.32%
Questions
Can I replace 265/40R21 with 265/45R20?
265/45R20 is a safe swap for 265/40R21 by the usual ±3% rule: the diameter differs by +0.15%.
What's the difference between 265/40R21 and 265/45R20?
265/45R20 is 0.04" taller and 0 mm wider; the sidewall is +0.52". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 265/45R20 fit on 265/40R21 wheels?
No — 265/40R21 needs a 21" wheel and 265/45R20 a 20" wheel. This is a plus/minus-size swap that changes wheels too.