235/50R20 vs 265/40R21
265/40R21 is a safe swap for 235/50R20 by the usual ±3% rule: the diameter differs by +0.32%.
Speedometer and odometer
With 265/40R21 on a car calibrated for 235/50R20, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.3%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.2 mph |
| 70 mph | 70.2 mph |
| 80 mph | 80.3 mph |
Other sizes close to 235/50R20
- 235/50R20 vs 235/55R19-0.26%
- 235/50R20 vs 245/45R20-1.95%
- 235/50R20 vs 255/45R20-0.74%
- 235/50R20 vs 255/50R19-0.73%
- 235/50R20 vs 275/40R20-2.02%
- 235/50R20 vs 255/50R20+2.69%
- 235/50R20 vs 265/50R20+4.04%
- 235/50R20 vs 245/50R20+1.35%
- 235/50R20 vs 275/45R20+1.68%
- 235/50R20 vs 235/55R20+3.16%
- 235/50R20 vs 255/40R20-4.17%
- 235/50R20 vs 265/45R20+0.47%
Questions
Can I replace 235/50R20 with 265/40R21?
265/40R21 is a safe swap for 235/50R20 by the usual ±3% rule: the diameter differs by +0.32%.
What's the difference between 235/50R20 and 265/40R21?
265/40R21 is 0.09" taller and 30 mm wider; the sidewall is -0.45". At an indicated 60 mph you'd actually be doing 60.2 mph.
Will 265/40R21 fit on 235/50R20 wheels?
No — 235/50R20 needs a 20" wheel and 265/40R21 a 21" wheel. This is a plus/minus-size swap that changes wheels too.