285/70R17 vs 315/70R17
315/70R17 is 1.65 in (5.06%) taller than 285/70R17. Edit either size below to try other combinations.
Metric (265/70R17) or inch (33x12.50R20). Axle ratio is used for the RPM table only.
315/70R17 is 1.65 in (42 mm) taller than 285/70R17 (+5.1%). With a speedometer calibrated for 285/70R17, an indicated 60 mph is really 63.0 mph. The diameter difference is more than ±3%, a range often quoted as a rule of thumb, so speedometer, gearing and clearance effects are larger.
Geometry only: this does not confirm that a size fits, is approved for or is safe on a particular vehicle. Wheel width and offset, suspension, clearances, load index, speed rating, the vehicle maker's specification and local regulations all apply — check with your owner's manual and a qualified tire professional.
| 285/70R17 | 315/70R17 | Difference | |
|---|---|---|---|
| Diameter | 32.71 in | 34.36 in | +1.65 in (+5.06%) |
| Diameter (mm) | 831 mm | 873 mm | +42 mm |
| Width | 11.22 in | 12.40 in | +1.18 in (+30 mm) |
| Sidewall | 7.85 in | 8.68 in | +0.83 in |
| Rim | 17 in | 17 in | ±0.0 in |
| Circumference | 102.8 in | 108.0 in | +5.19 in |
| Revs per mile | 617 | 587 | −30 |
| Ground clearance change | — | — | +0.83 in |
Speedometer error
| Speedometer shows | True speed on 315/70R17 | Difference |
|---|---|---|
| 20 mph | 21.0 mph | +1.0 mph |
| 30 mph | 31.5 mph | +1.5 mph |
| 40 mph | 42.0 mph | +2.0 mph |
| 50 mph | 52.5 mph | +2.5 mph |
| 60 mph | 63.0 mph | +3.0 mph |
| 70 mph | 73.5 mph | +3.5 mph |
| 80 mph | 84.0 mph | +4.0 mph |
| Speedometer shows | True speed on 315/70R17 | Difference |
|---|---|---|
| 30 km/h | 31.5 km/h | +1.5 km/h |
| 50 km/h | 52.5 km/h | +2.5 km/h |
| 80 km/h | 84.0 km/h | +4.0 km/h |
| 100 km/h | 105.1 km/h | +5.1 km/h |
| 120 km/h | 126.1 km/h | +6.1 km/h |
Assumes the speedometer was accurate on 285/70R17. Factory speedometers often read slightly high on purpose; check against GPS.
Engine RPM and gearing
| Road speed | 285/70R17 | 315/70R17 | Change |
|---|---|---|---|
| 45 mph | 1,725 rpm | 1,642 rpm | −83 rpm |
| 55 mph | 2,108 rpm | 2,007 rpm | −101 rpm |
| 65 mph | 2,492 rpm | 2,372 rpm | −120 rpm |
| 75 mph | 2,875 rpm | 2,737 rpm | −138 rpm |
To restore the original effective gearing on 315/70R17 you would need an axle ratio of about 3.92 (nearest ratios on our reference list: 3.91 or 4.10). For overdrive gears multiply the RPM by the gear ratio (e.g. ×0.69).
Other 17-inch sizes within ±3% of 285/70R17
| Size | Diameter | Width | vs original |
|---|---|---|---|
| 235/85R17 | 32.73 in | 9.25 in | +0.06% |
| 265/75R17 | 32.65 in | 10.43 in | −0.18% |
| 305/65R17 | 32.61 in | 12.01 in | −0.30% |
| 335/60R17 | 32.83 in | 13.19 in | +0.36% |
| 245/80R17 | 32.43 in | 9.65 in | −0.84% |
| 355/55R17 | 32.37 in | 13.98 in | −1.02% |
| 255/80R17 | 33.06 in | 10.04 in | +1.08% |
| 325/60R17 | 32.35 in | 12.80 in | −1.08% |
Computed combinations of standard widths and aspect ratios; not every size is manufactured. A similar diameter does not mean a size fits or is approved for your vehicle.
What changes if you switch
- The 5.06% height difference is more than the ±3% often quoted as a rule of thumb; a speedometer calibrated for 285/70R17 reads about 4.8% low, and clearance at full steering lock and suspension travel changes more.
- 315/70R17 is 30 mm (1.18 in) wider in nominal section width. Width affects clearance to suspension, frame and body parts and which rim widths the tire maker approves; actual clearance depends on the wheel offset and the vehicle.
- Both sizes are made for 17-inch wheels. Whether a given wheel's width and offset suit 315/70R17 has to be checked against the tire maker's approved rim widths and the vehicle.
- Ground clearance under the axles increases by about 0.83 in (half the height difference).
- Sidewall height goes from 7.85 in to 8.68 in. Taller sidewalls generally flex more; ride and handling also depend on the tire's construction and pressure.
Size pages
Related comparisons
Frequently asked questions
Is 315/70R17 bigger than 285/70R17?
315/70R17 is 1.65 in (42 mm, 5.06%) taller than 285/70R17.
Can I replace 285/70R17 with 315/70R17?
This page can only compare dimensions: the diameter difference is 5.06%, more than the ±3% often quoted as a rule of thumb. It cannot tell you whether 315/70R17 fits or is approved for your vehicle — that depends on wheel width and offset, suspension and body clearance, the load index and speed rating your vehicle requires, and local regulations. Check your owner's manual and placard and ask a qualified tire professional.
How much does the speedometer change from 285/70R17 to 315/70R17?
It reads low by about 4.81% of the indicated speed: at an indicated 60 mph you are actually doing 63.0 mph (at 100 km/h, 105.1 km/h).
How does 315/70R17 change engine RPM?
Example with a 3.73 axle ratio in direct drive at 65 mph: 2492 rpm on 285/70R17 and 2372 rpm on 315/70R17. Restoring the original effective gearing would take an axle ratio of about 3.92. Enter your own axle ratio in the tool above; this is arithmetic, not a recommendation to change gears.
Nominal geometry for planning only; not fitment advice. See methodology.
Related tools
- Speedometer error calculator
How fast you are really going after a tire change.
- Gear ratio & RPM
Engine RPM and the regear needed for bigger tires.
- Plus size calculator
Sizes that keep your diameter on a bigger or smaller wheel.
- Inch ↔ metric converter
33x12.50R17 to metric and back, with closest equivalents.