305/65R18 vs 35x12.50R18
35x12.50R18 is outside the ±3% rule as a replacement for 305/65R18: the diameter differs by +4.13%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Side by side
| 305/65R18 | 35x12.50R18 | Difference | |
|---|---|---|---|
| Overall diameter | 33.61" | 35.00" | +1.39" (+4.13%) |
| Section width | 305 mm | 318 mm | +13 mm |
| Sidewall | 7.81" | 8.50" | +0.69" |
| Rim | 18" | 18" | same |
| Circumference | 105.6" | 110.0" | +4.4" |
| Revs per mile | 600 | 576 | -24 |
| Ride height | — | — | +0.69" |
| Speedometer reads 60 mph | 60.0 | 62.5 | +2.5 mph |
Speedometer and odometer
With 35x12.50R18 on a car calibrated for 305/65R18, the speedometer reads 57.6 mph when you're really doing 60, and the odometer under-counts by 4.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.2 mph |
| 45 mph | 46.9 mph |
| 60 mph | 62.5 mph |
| 70 mph | 72.9 mph |
| 80 mph | 83.3 mph |
Other sizes close to 305/65R18
- 305/65R18 vs 275/65R18-4.57%
- 305/65R18 vs 275/70R18-1.35%
- 305/65R18 vs 265/70R18-2.99%
- 305/65R18 vs 255/70R18-4.63%
- 305/65R18 vs 285/65R18-3.05%
- 305/65R18 vs 295/70R18+1.93%
- 305/65R18 vs 33x12.50R18-1.82%
- 305/65R18 vs 285/75R17+0.66%
- 305/65R18 vs 285/75R18+3.63%
- 305/65R18 vs 325/65R18+3.05%
- 305/65R18 vs 305/70R18+3.57%
- 305/65R18 vs 285/70R18+0.29%
Questions
Can I replace 305/65R18 with 35x12.50R18?
35x12.50R18 is outside the ±3% rule as a replacement for 305/65R18: the diameter differs by +4.13%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 305/65R18 and 35x12.50R18?
35x12.50R18 is 1.39" taller and 13 mm wider; the sidewall is +0.69". At an indicated 60 mph you'd actually be doing 62.5 mph.
Will 35x12.50R18 fit on 305/65R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 318 mm tire and the fender clearance.