255/70R18 vs 285/65R18
285/65R18 is taller than 255/70R18 by 1.66% — a diameter difference of 0.53″.
What changes between 255/70R18 and 285/65R18
Switching from 255/70R18 to 285/65R18 changes overall diameter by +1.66%, a taller tire by 0.53 inches. This lands inside the ±3% fitment safe zone, so most vehicles will accept the swap without rubbing, speedometer recalibration, or ABS/TPMS complications. Section width moves by +1.18″ (255mm → 285mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.26″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -10, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.1 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 255/70R18 | 285/65R18 |
|---|---|---|
| Overall diameter | 32.06″ | 32.59″ |
| Section width | 10.04″ (255 mm) | 11.22″ (285 mm) |
| Sidewall height | 7.03″ (70%) | 7.29″ (65%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 100.7″ | 102.37″ |
| Revs per mile | 629 | 619 |
Interactive comparison
275/65R18 or "33" for inch aliases255/70R18
- Diameter
- 32.06″ / 814.2mm
- Section Width
- 10.04″
- Sidewall
- 7.03″ / 178.5mm
- Circumference
- 100.7″
- Revs/Mile
- 629
285/65R18
- Diameter
- 32.59″ / 827.7mm
- Section Width
- 11.22″
- Sidewall
- 7.29″ / 185.25mm
- Circumference
- 102.37″
- Revs/Mile
- 619
Speedometer & Diameter Impact
Wider tire — verify wheel widthAt an indicated 60 mph, your actual speed is 60.99 mph (98.16 km/h). Your speedometer reads 1.66% low versus actual speed.