275/30R21 vs 275/35R20
275/35R20 is a safe swap for 275/30R21 by the usual ±3% rule: the diameter differs by +0.30%.
Speedometer and odometer
With 275/35R20 on a car calibrated for 275/30R21, 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 | 80.2 mph |
Other sizes close to 275/30R21
- 275/30R21 vs 245/40R20+0.80%
- 275/30R21 vs 265/35R20-0.70%
- 275/30R21 vs 275/35R21+3.94%
- 275/30R21 vs 265/35R21+2.94%
- 275/30R21 vs 245/35R21+0.93%
- 275/30R21 vs 325/30R21+4.30%
- 275/30R21 vs 255/35R21+1.93%
- 275/30R21 vs 315/30R21+3.44%
- 275/30R21 vs 285/35R21+4.94%
- 275/30R21 vs 245/40R21+4.44%
- 275/30R21 vs 295/30R21+1.72%
- 275/30R21 vs 305/30R21+2.58%
Questions
Can I replace 275/30R21 with 275/35R20?
275/35R20 is a safe swap for 275/30R21 by the usual ±3% rule: the diameter differs by +0.30%.
What's the difference between 275/30R21 and 275/35R20?
275/35R20 is 0.08" taller and 0 mm wider; the sidewall is +0.54". At an indicated 60 mph you'd actually be doing 60.2 mph.
Will 275/35R20 fit on 275/30R21 wheels?
No — 275/30R21 needs a 21" wheel and 275/35R20 a 20" wheel. This is a plus/minus-size swap that changes wheels too.