185/65R15 vs 185/70R15
185/70R15 is taller than 185/65R15 by 2.98% — a diameter difference of 0.73″.
What changes between 185/65R15 and 185/70R15
Switching from 185/65R15 to 185/70R15 changes overall diameter by +2.98%, a taller tire by 0.73 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 0.00″ (185mm → 185mm), 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 -24, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.9 mph. Both sizes share the same 15″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 185/65R15 | 185/70R15 |
|---|---|---|
| Overall diameter | 24.47″ | 25.2″ |
| Section width | 7.28″ (185 mm) | 7.28″ (185 mm) |
| Sidewall height | 4.73″ (65%) | 5.1″ (70%) |
| Rim diameter | 15″ | 15″ |
| Circumference | 76.87″ | 79.16″ |
| Revs per mile | 824 | 800 |
Interactive comparison
275/65R18 or "33" for inch aliases185/65R15
- Diameter
- 24.47″ / 621.5mm
- Section Width
- 7.28″
- Sidewall
- 4.73″ / 120.25mm
- Circumference
- 76.87″
- Revs/Mile
- 824
185/70R15
- Diameter
- 25.2″ / 640mm
- Section Width
- 7.28″
- Sidewall
- 5.1″ / 129.5mm
- Circumference
- 79.16″
- Revs/Mile
- 800
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.79 mph (99.43 km/h). Your speedometer reads 2.98% low versus actual speed.