265/45R21 vs 285/45R21
285/45R21 is taller than 265/45R21 by 2.33% — a diameter difference of 0.71″.
What changes between 265/45R21 and 285/45R21
Switching from 265/45R21 to 285/45R21 changes overall diameter by +2.33%, a taller tire by 0.71 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 +0.79″ (265mm → 285mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.36″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -15, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.5 mph. Both sizes share the same 21″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 265/45R21 | 285/45R21 |
|---|---|---|
| Overall diameter | 30.39″ | 31.1″ |
| Section width | 10.43″ (265 mm) | 11.22″ (285 mm) |
| Sidewall height | 4.69″ (45%) | 5.05″ (45%) |
| Rim diameter | 21″ | 21″ |
| Circumference | 95.47″ | 97.7″ |
| Revs per mile | 664 | 649 |
Interactive comparison
275/65R18 or "33" for inch aliases265/45R21
- Diameter
- 30.39″ / 771.9mm
- Section Width
- 10.43″
- Sidewall
- 4.69″ / 119.25mm
- Circumference
- 95.47″
- Revs/Mile
- 664
285/45R21
- Diameter
- 31.1″ / 789.9mm
- Section Width
- 11.22″
- Sidewall
- 5.05″ / 128.25mm
- Circumference
- 97.7″
- Revs/Mile
- 649
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.4 mph (98.81 km/h). Your speedometer reads 2.33% low versus actual speed.