235/85R16 vs 305/70R16
305/70R16 is outside the ±3% rule as a replacement for 235/85R16: the diameter differs by +3.41%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 305/70R16 on a car calibrated for 235/85R16, the speedometer reads 58.0 mph when you're really doing 60, and the odometer under-counts by 3.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.0 mph |
| 45 mph | 46.5 mph |
| 60 mph | 62.0 mph |
| 70 mph | 72.4 mph |
| 80 mph | 82.7 mph |
Other sizes close to 235/85R16
- 235/85R16 vs 265/70R17-0.38%
- 235/85R16 vs 265/75R16-0.25%
- 235/85R16 vs 245/75R16-3.97%
- 235/85R16 vs 245/75R17-0.82%
- 235/85R16 vs 265/70R16-3.54%
- 235/85R16 vs 235/80R17+0.24%
- 235/85R16 vs 285/75R16+3.47%
- 235/85R16 vs 215/85R16-4.22%
- 235/85R16 vs 32x11.50R15+0.86%
- 235/85R16 vs 275/70R16-1.80%
- 235/85R16 vs 255/85R16+4.22%
Questions
Can I replace 235/85R16 with 305/70R16?
305/70R16 is outside the ±3% rule as a replacement for 235/85R16: the diameter differs by +3.41%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 235/85R16 and 305/70R16?
305/70R16 is 1.08" taller and 70 mm wider; the sidewall is +0.54". At an indicated 60 mph you'd actually be doing 62.0 mph.
Will 305/70R16 fit on 235/85R16 wheels?
Both use a 16" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.