265/35R21 vs 305/35R21
305/35R21 is taller than 265/35R21 by 3.89% — a diameter difference of 1.11″.
What changes between 265/35R21 and 305/35R21
Switching from 265/35R21 to 305/35R21 changes overall diameter by +3.89%, a taller tire by 1.11 inches. This sits in the 3–5% caution band, where rubbing at full steering lock or suspension compression becomes possible. Leveling kits or fender-liner trims are often needed on lifted trucks. Section width moves by +1.58″ (265mm → 305mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.55″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -27, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 67.5 mph. Both sizes share the same 21″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 265/35R21 | 305/35R21 |
|---|---|---|
| Overall diameter | 28.3″ | 29.41″ |
| Section width | 10.43″ (265 mm) | 12.01″ (305 mm) |
| Sidewall height | 3.65″ (35%) | 4.2″ (35%) |
| Rim diameter | 21″ | 21″ |
| Circumference | 88.92″ | 92.38″ |
| Revs per mile | 713 | 686 |
Interactive comparison
275/65R18 or "33" for inch aliases265/35R21
- Diameter
- 28.3″ / 718.9mm
- Section Width
- 10.43″
- Sidewall
- 3.65″ / 92.75mm
- Circumference
- 88.92″
- Revs/Mile
- 713
305/35R21
- Diameter
- 29.41″ / 746.9mm
- Section Width
- 12.01″
- Sidewall
- 4.2″ / 106.75mm
- Circumference
- 92.38″
- Revs/Mile
- 686
Speedometer & Diameter Impact
Wider tire — verify wheel widthAt an indicated 60 mph, your actual speed is 62.34 mph (100.32 km/h). Your speedometer reads 3.89% low versus actual speed.