285/60R18 vs 255/70R18
255/70R18 is taller than 285/60R18 by 1.88% — a diameter difference of 0.60″.
What changes between 285/60R18 and 255/70R18
Switching from 285/60R18 to 255/70R18 changes overall diameter by +1.88%, a taller tire by 0.60 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″ (285mm → 255mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.30″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -12, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.2 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 285/60R18 | 255/70R18 |
|---|---|---|
| Overall diameter | 31.46″ | 32.06″ |
| Section width | 11.22″ (285 mm) | 10.04″ (255 mm) |
| Sidewall height | 6.73″ (60%) | 7.03″ (70%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 98.85″ | 100.7″ |
| Revs per mile | 641 | 629 |
Interactive comparison
275/65R18 or "33" for inch aliases285/60R18
- Diameter
- 31.46″ / 799.2mm
- Section Width
- 11.22″
- Sidewall
- 6.73″ / 171mm
- Circumference
- 98.85″
- Revs/Mile
- 641
255/70R18
- Diameter
- 32.06″ / 814.2mm
- Section Width
- 10.04″
- Sidewall
- 7.03″ / 178.5mm
- Circumference
- 100.7″
- Revs/Mile
- 629
Speedometer & Diameter Impact
Narrower tire — verify wheel widthAt an indicated 60 mph, your actual speed is 61.13 mph (98.37 km/h). Your speedometer reads 1.88% low versus actual speed.