245/35R20 vs 305/30R20
305/30R20 is a safe swap for 245/35R20 by the usual ±3% rule: the diameter differs by +1.69%.
Speedometer and odometer
With 305/30R20 on a car calibrated for 245/35R20, the speedometer reads 59.0 mph when you're really doing 60, and the odometer under-counts by 1.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.5 mph |
| 45 mph | 45.8 mph |
| 60 mph | 61.0 mph |
| 70 mph | 71.2 mph |
| 80 mph | 81.4 mph |
Other sizes close to 245/35R20
- 245/35R20 vs 245/40R19-0.13%
- 245/35R20 vs 245/40R20+3.61%
- 245/35R20 vs 275/35R19-0.65%
- 245/35R20 vs 255/35R20+1.03%
- 245/35R20 vs 275/35R20+3.09%
- 245/35R20 vs 255/40R20+4.78%
- 245/35R20 vs 225/45R19+0.82%
- 245/35R20 vs 285/35R19+0.38%
- 245/35R20 vs 285/35R20+4.12%
- 245/35R20 vs 285/30R20-0.07%
- 245/35R20 vs 275/30R20-0.96%
- 245/35R20 vs 265/35R20+2.06%
Questions
Can I replace 245/35R20 with 305/30R20?
305/30R20 is a safe swap for 245/35R20 by the usual ±3% rule: the diameter differs by +1.69%.
What's the difference between 245/35R20 and 305/30R20?
305/30R20 is 0.45" taller and 60 mm wider; the sidewall is +0.23". At an indicated 60 mph you'd actually be doing 61.0 mph.
Will 305/30R20 fit on 245/35R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.