245/70R17 vs 255/70R17
255/70R17 is taller than 245/70R17 by 1.81% — a diameter difference of 0.56″.
What changes between 245/70R17 and 255/70R17
Switching from 245/70R17 to 255/70R17 changes overall diameter by +1.81%, a taller tire by 0.56 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 +0.39″ (245mm → 255mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.28″: 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 66.2 mph. Both sizes share the same 17″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 245/70R17 | 255/70R17 |
|---|---|---|
| Overall diameter | 30.5″ | 31.06″ |
| Section width | 9.65″ (245 mm) | 10.04″ (255 mm) |
| Sidewall height | 6.75″ (70%) | 7.03″ (70%) |
| Rim diameter | 17″ | 17″ |
| Circumference | 95.83″ | 97.56″ |
| Revs per mile | 661 | 649 |
Interactive comparison
275/65R18 or "33" for inch aliases245/70R17
- Diameter
- 30.5″ / 774.8mm
- Section Width
- 9.65″
- Sidewall
- 6.75″ / 171.5mm
- Circumference
- 95.83″
- Revs/Mile
- 661
255/70R17
- Diameter
- 31.06″ / 788.8mm
- Section Width
- 10.04″
- Sidewall
- 7.03″ / 178.5mm
- Circumference
- 97.56″
- Revs/Mile
- 649
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.08 mph (98.31 km/h). Your speedometer reads 1.81% low versus actual speed.