255/70R17 vs 235/80R17
235/80R17 is taller than 255/70R17 by 2.41% — a diameter difference of 0.74″.
What changes between 255/70R17 and 235/80R17
Switching from 255/70R17 to 235/80R17 changes overall diameter by +2.41%, a taller tire by 0.74 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 -0.79″ (255mm → 235mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.37″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -15, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.6 mph. Both sizes share the same 17″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 255/70R17 | 235/80R17 |
|---|---|---|
| Overall diameter | 31.06″ | 31.8″ |
| Section width | 10.04″ (255 mm) | 9.25″ (235 mm) |
| Sidewall height | 7.03″ (70%) | 7.4″ (80%) |
| Rim diameter | 17″ | 17″ |
| Circumference | 97.56″ | 99.91″ |
| Revs per mile | 649 | 634 |
Interactive comparison
275/65R18 or "33" for inch aliases255/70R17
- Diameter
- 31.06″ / 788.8mm
- Section Width
- 10.04″
- Sidewall
- 7.03″ / 178.5mm
- Circumference
- 97.56″
- Revs/Mile
- 649
235/80R17
- Diameter
- 31.8″ / 807.8mm
- Section Width
- 9.25″
- Sidewall
- 7.4″ / 188mm
- Circumference
- 99.91″
- Revs/Mile
- 634
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.45 mph (98.89 km/h). Your speedometer reads 2.41% low versus actual speed.