235/65R18 vs 245/65R18
245/65R18 is taller than 235/65R18 by 1.70% — a diameter difference of 0.51″.
What changes between 235/65R18 and 245/65R18
Switching from 235/65R18 to 245/65R18 changes overall diameter by +1.70%, a taller tire by 0.51 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″ (235mm → 245mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.26″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -12, 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 | 235/65R18 | 245/65R18 |
|---|---|---|
| Overall diameter | 30.03″ | 30.54″ |
| Section width | 9.25″ (235 mm) | 9.65″ (245 mm) |
| Sidewall height | 6.01″ (65%) | 6.27″ (65%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 94.33″ | 95.94″ |
| Revs per mile | 672 | 660 |
Interactive comparison
275/65R18 or "33" for inch aliases235/65R18
- Diameter
- 30.03″ / 762.7mm
- Section Width
- 9.25″
- Sidewall
- 6.01″ / 152.75mm
- Circumference
- 94.33″
- Revs/Mile
- 672
245/65R18
- Diameter
- 30.54″ / 775.7mm
- Section Width
- 9.65″
- Sidewall
- 6.27″ / 159.25mm
- Circumference
- 95.94″
- Revs/Mile
- 660
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.02 mph (98.21 km/h). Your speedometer reads 1.70% low versus actual speed.