265/45R21 vs 275/45R21
275/45R21 is taller than 265/45R21 by 1.17% — a diameter difference of 0.35″.
What changes between 265/45R21 and 275/45R21
Switching from 265/45R21 to 275/45R21 changes overall diameter by +1.17%, a taller tire by 0.35 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 +0.40″ (265mm → 275mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.18″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -8, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 65.8 mph. Both sizes share the same 21″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 265/45R21 | 275/45R21 |
|---|---|---|
| Overall diameter | 30.39″ | 30.74″ |
| Section width | 10.43″ (265 mm) | 10.83″ (275 mm) |
| Sidewall height | 4.69″ (45%) | 4.87″ (45%) |
| Rim diameter | 21″ | 21″ |
| Circumference | 95.47″ | 96.59″ |
| Revs per mile | 664 | 656 |
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
275/45R21
- Diameter
- 30.74″ / 780.9mm
- Section Width
- 10.83″
- Sidewall
- 4.87″ / 123.75mm
- Circumference
- 96.59″
- Revs/Mile
- 656
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 60.7 mph (97.69 km/h). Your speedometer reads 1.17% low versus actual speed.