305/70R17 vs 35x12.50R17
35x12.50R17 is outside the ±3% rule as a replacement for 305/70R17: the diameter differs by +3.52%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Side by side
| 305/70R17 | 35x12.50R17 | Difference | |
|---|---|---|---|
| Overall diameter | 33.81" | 35.00" | +1.19" (+3.52%) |
| Section width | 305 mm | 318 mm | +13 mm |
| Sidewall | 8.41" | 9.00" | +0.59" |
| Rim | 17" | 17" | same |
| Circumference | 106.2" | 110.0" | +3.7" |
| Revs per mile | 596 | 576 | -20 |
| Ride height | — | — | +0.59" |
| Speedometer reads 60 mph | 60.0 | 62.1 | +2.1 mph |
Speedometer and odometer
With 35x12.50R17 on a car calibrated for 305/70R17, the speedometer reads 58.0 mph when you're really doing 60, and the odometer under-counts by 3.5%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.1 mph |
| 45 mph | 46.6 mph |
| 60 mph | 62.1 mph |
| 70 mph | 72.5 mph |
| 80 mph | 82.8 mph |
Other sizes close to 305/70R17
Questions
Can I replace 305/70R17 with 35x12.50R17?
35x12.50R17 is outside the ±3% rule as a replacement for 305/70R17: the diameter differs by +3.52%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 305/70R17 and 35x12.50R17?
35x12.50R17 is 1.19" taller and 13 mm wider; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 62.1 mph.
Will 35x12.50R17 fit on 305/70R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 318 mm tire and the fender clearance.