265/40R20 vs 235/50R20
235/50R20 is outside the ±3% rule as a replacement for 265/40R20: the diameter differs by +3.19%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 235/50R20 on a car calibrated for 265/40R20, the speedometer reads 58.1 mph when you're really doing 60, and the odometer under-counts by 3.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.0 mph |
| 45 mph | 46.4 mph |
| 60 mph | 61.9 mph |
| 70 mph | 72.2 mph |
| 80 mph | 82.6 mph |
Other sizes close to 265/40R20
- 265/40R20 vs 245/45R20+1.18%
- 265/40R20 vs 255/45R20+2.43%
- 265/40R20 vs 275/40R20+1.11%
- 265/40R20 vs 245/40R20-2.22%
- 265/40R20 vs 245/50R20+4.58%
- 265/40R20 vs 275/45R20+4.93%
- 265/40R20 vs 255/35R20-4.65%
- 265/40R20 vs 255/40R20-1.11%
- 265/40R20 vs 275/35R20-2.71%
- 265/40R20 vs 235/50R19-0.33%
- 265/40R20 vs 265/45R20+3.68%
- 265/40R20 vs 285/35R20-1.74%
Questions
Can I replace 265/40R20 with 235/50R20?
235/50R20 is outside the ±3% rule as a replacement for 265/40R20: the diameter differs by +3.19%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 265/40R20 and 235/50R20?
235/50R20 is 0.91" taller and 30 mm narrower; the sidewall is +0.45". At an indicated 60 mph you'd actually be doing 61.9 mph.
Will 235/50R20 fit on 265/40R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 235 mm tire and the fender clearance.