265/35R20 vs 275/30R21
275/30R21 is a safe swap for 265/35R20 by the usual ±3% rule: the diameter differs by +0.71%.
Speedometer and odometer
With 275/30R21 on a car calibrated for 265/35R20, 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 265/35R20
- 265/35R20 vs 255/40R19-0.99%
- 265/35R20 vs 275/40R20+4.97%
- 265/35R20 vs 245/40R20+1.51%
- 265/35R20 vs 245/35R20-2.02%
- 265/35R20 vs 255/35R20-1.01%
- 265/35R20 vs 275/35R20+1.01%
- 265/35R20 vs 255/40R20+2.67%
- 265/35R20 vs 235/45R19+0.09%
- 265/35R20 vs 285/35R20+2.02%
- 265/35R20 vs 285/30R20-2.09%
- 265/35R20 vs 275/30R20-2.96%
- 265/35R20 vs 235/35R20-3.03%
Questions
Can I replace 265/35R20 with 275/30R21?
275/30R21 is a safe swap for 265/35R20 by the usual ±3% rule: the diameter differs by +0.71%.
What's the difference between 265/35R20 and 275/30R21?
275/30R21 is 0.19" taller and 10 mm wider; the sidewall is -0.40". At an indicated 60 mph you'd actually be doing 60.4 mph.
Will 275/30R21 fit on 265/35R20 wheels?
No — 265/35R20 needs a 20" wheel and 275/30R21 a 21" wheel. This is a plus/minus-size swap that changes wheels too.