30x9.50R15 vs 255/70R16
255/70R16 is a safe swap for 30x9.50R15 by the usual ±3% rule: the diameter differs by +0.18%.
Side by side
| 30x9.50R15 | 255/70R16 | Difference | |
|---|---|---|---|
| Overall diameter | 30.00" | 30.06" | +0.06" (+0.18%) |
| Section width | 241 mm | 255 mm | +14 mm |
| Sidewall | 7.50" | 7.03" | -0.47" |
| Rim | 15" | 16" | +1" |
| Circumference | 94.2" | 94.4" | +0.2" |
| Revs per mile | 672 | 671 | -1 |
| Ride height | — | — | +0.03" |
| Speedometer reads 60 mph | 60.0 | 60.1 | +0.1 mph |
Speedometer and odometer
With 255/70R16 on a car calibrated for 30x9.50R15, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.1 mph |
| 70 mph | 70.1 mph |
| 80 mph | 80.1 mph |
Other sizes close to 30x9.50R15
Questions
Can I replace 30x9.50R15 with 255/70R16?
255/70R16 is a safe swap for 30x9.50R15 by the usual ±3% rule: the diameter differs by +0.18%.
What's the difference between 30x9.50R15 and 255/70R16?
255/70R16 is 0.06" taller and 14 mm wider; the sidewall is -0.47". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 255/70R16 fit on 30x9.50R15 wheels?
No — 30x9.50R15 needs a 15" wheel and 255/70R16 a 16" wheel. This is a plus/minus-size swap that changes wheels too.