285/65R18 vs 275/70R18
275/70R18 is taller than 285/65R18 by 1.75% — a diameter difference of 0.57″.
What changes between 285/65R18 and 275/70R18
Switching from 285/65R18 to 275/70R18 changes overall diameter by +1.75%, a taller tire by 0.57 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 -0.39″ (285mm → 275mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.29″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -11, 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 | 285/65R18 | 275/70R18 |
|---|---|---|
| Overall diameter | 32.59″ | 33.16″ |
| Section width | 11.22″ (285 mm) | 10.83″ (275 mm) |
| Sidewall height | 7.29″ (65%) | 7.58″ (70%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 102.37″ | 104.17″ |
| Revs per mile | 619 | 608 |
Interactive comparison
275/65R18 or "33" for inch aliases285/65R18
- Diameter
- 32.59″ / 827.7mm
- Section Width
- 11.22″
- Sidewall
- 7.29″ / 185.25mm
- Circumference
- 102.37″
- Revs/Mile
- 619
275/70R18
- Diameter
- 33.16″ / 842.2mm
- Section Width
- 10.83″
- Sidewall
- 7.58″ / 192.5mm
- Circumference
- 104.17″
- Revs/Mile
- 608
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.05 mph (98.25 km/h). Your speedometer reads 1.75% low versus actual speed.