305/70R16 vs 33x12.50R15
33x12.50R15 is a safe swap for 305/70R16 by the usual ±3% rule: the diameter differs by +0.58%.
Side by side
| 305/70R16 | 33x12.50R15 | Difference | |
|---|---|---|---|
| Overall diameter | 32.81" | 33.00" | +0.19" (+0.58%) |
| Section width | 305 mm | 318 mm | +13 mm |
| Sidewall | 8.41" | 9.00" | +0.59" |
| Rim | 16" | 15" | -1" |
| Circumference | 103.1" | 103.7" | +0.6" |
| Revs per mile | 615 | 611 | -4 |
| Ride height | — | — | +0.09" |
| Speedometer reads 60 mph | 60.0 | 60.3 | +0.3 mph |
Speedometer and odometer
With 33x12.50R15 on a car calibrated for 305/70R16, the speedometer reads 59.7 mph when you're really doing 60, and the odometer under-counts by 0.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.3 mph |
| 60 mph | 60.3 mph |
| 70 mph | 70.4 mph |
| 80 mph | 80.5 mph |
Other sizes close to 305/70R16
Questions
Can I replace 305/70R16 with 33x12.50R15?
33x12.50R15 is a safe swap for 305/70R16 by the usual ±3% rule: the diameter differs by +0.58%.
What's the difference between 305/70R16 and 33x12.50R15?
33x12.50R15 is 0.19" taller and 13 mm wider; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 60.3 mph.
Will 33x12.50R15 fit on 305/70R16 wheels?
No — 305/70R16 needs a 16" wheel and 33x12.50R15 a 15" wheel. This is a plus/minus-size swap that changes wheels too.