235/55R20 vs 295/40R21
295/40R21 is a safe swap for 235/55R20 by the usual ±3% rule: the diameter differs by +0.38%.
Speedometer and odometer
With 295/40R21 on a car calibrated for 235/55R20, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.2 mph |
| 60 mph | 60.2 mph |
| 70 mph | 70.3 mph |
| 80 mph | 80.3 mph |
Other sizes close to 235/55R20
- 235/55R20 vs 245/45R20-4.96%
- 235/55R20 vs 255/45R20-3.78%
- 235/55R20 vs 255/50R20-0.46%
- 235/55R20 vs 265/50R20+0.85%
- 235/55R20 vs 245/50R20-1.76%
- 235/55R20 vs 275/45R20-1.44%
- 235/55R20 vs 255/55R20+2.87%
- 235/55R20 vs 265/45R20-2.61%
- 235/55R20 vs 255/55R19-0.44%
- 235/55R20 vs 315/35R20-4.96%
- 235/55R20 vs 275/50R20+2.15%
- 235/55R20 vs 295/40R20-2.94%
Questions
Can I replace 235/55R20 with 295/40R21?
295/40R21 is a safe swap for 235/55R20 by the usual ±3% rule: the diameter differs by +0.38%.
What's the difference between 235/55R20 and 295/40R21?
295/40R21 is 0.11" taller and 60 mm wider; the sidewall is -0.44". At an indicated 60 mph you'd actually be doing 60.2 mph.
Will 295/40R21 fit on 235/55R20 wheels?
No — 235/55R20 needs a 20" wheel and 295/40R21 a 21" wheel. This is a plus/minus-size swap that changes wheels too.