265/35R21 vs 265/40R21
265/40R21 is taller than 265/35R21 by 3.69% — a diameter difference of 1.05″.
What changes between 265/35R21 and 265/40R21
Switching from 265/35R21 to 265/40R21 changes overall diameter by +3.69%, a taller tire by 1.05 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 0.00″ (265mm → 265mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.52″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -26, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 67.4 mph. Both sizes share the same 21″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 265/35R21 | 265/40R21 |
|---|---|---|
| Overall diameter | 28.3″ | 29.35″ |
| Section width | 10.43″ (265 mm) | 10.43″ (265 mm) |
| Sidewall height | 3.65″ (35%) | 4.17″ (40%) |
| Rim diameter | 21″ | 21″ |
| Circumference | 88.92″ | 92.19″ |
| Revs per mile | 713 | 687 |
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
265/40R21
- Diameter
- 29.35″ / 745.4mm
- Section Width
- 10.43″
- Sidewall
- 4.17″ / 106mm
- Circumference
- 92.19″
- Revs/Mile
- 687
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 62.21 mph (100.12 km/h). Your speedometer reads 3.69% low versus actual speed.