265/75R15 vs 31x10.50R15
31x10.50R15 is 0.35 in (1.14%) taller than 265/75R15. Edit either size below to try other combinations.
Metric (265/70R17) or inch (33x12.50R20). Axle ratio is used for the RPM table only.
31x10.50R15 is 0.35 in (9 mm) taller than 265/75R15 (+1.1%). With a speedometer calibrated for 265/75R15, an indicated 60 mph is really 60.7 mph. The diameter difference is within ±3%, a range often quoted as a rule of thumb for speedometer and gearing effects.
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.
| 265/75R15 | 31x10.50R15 | Difference | |
|---|---|---|---|
| Diameter | 30.65 in | 31.00 in | +0.35 in (+1.14%) |
| Diameter (mm) | 779 mm | 787 mm | +9 mm |
| Width | 10.43 in | 10.50 in | +0.07 in (+2 mm) |
| Sidewall | 7.82 in | 8.00 in | +0.18 in |
| Rim | 15 in | 15 in | ±0.0 in |
| Circumference | 96.3 in | 97.4 in | +1.10 in |
| Revs per mile | 658 | 651 | −7 |
| Ground clearance change | — | — | +0.18 in |
Speedometer error
| Speedometer shows | True speed on 31x10.50R15 | Difference |
|---|---|---|
| 20 mph | 20.2 mph | +0.2 mph |
| 30 mph | 30.3 mph | +0.3 mph |
| 40 mph | 40.5 mph | +0.5 mph |
| 50 mph | 50.6 mph | +0.6 mph |
| 60 mph | 60.7 mph | +0.7 mph |
| 70 mph | 70.8 mph | +0.8 mph |
| 80 mph | 80.9 mph | +0.9 mph |
| Speedometer shows | True speed on 31x10.50R15 | Difference |
|---|---|---|
| 30 km/h | 30.3 km/h | +0.3 km/h |
| 50 km/h | 50.6 km/h | +0.6 km/h |
| 80 km/h | 80.9 km/h | +0.9 km/h |
| 100 km/h | 101.1 km/h | +1.1 km/h |
| 120 km/h | 121.4 km/h | +1.4 km/h |
Assumes the speedometer was accurate on 265/75R15. Factory speedometers often read slightly high on purpose; check against GPS.
Engine RPM and gearing
| Road speed | 265/75R15 | 31x10.50R15 | Change |
|---|---|---|---|
| 45 mph | 1,841 rpm | 1,820 rpm | −21 rpm |
| 55 mph | 2,250 rpm | 2,224 rpm | −26 rpm |
| 65 mph | 2,659 rpm | 2,629 rpm | −30 rpm |
| 75 mph | 3,068 rpm | 3,033 rpm | −35 rpm |
To restore the original effective gearing on 31x10.50R15 you would need an axle ratio of about 3.77 — practically the same as now. For overdrive gears multiply the RPM by the gear ratio (e.g. ×0.69).
Other 15-inch sizes within ±3% of 265/75R15
| Size | Diameter | Width | vs original |
|---|---|---|---|
| 305/65R15 | 30.61 in | 12.01 in | −0.13% |
| 285/70R15 | 30.71 in | 11.22 in | +0.19% |
| 235/85R15 | 30.73 in | 9.25 in | +0.26% |
| 335/60R15 | 30.83 in | 13.19 in | +0.58% |
| 245/80R15 | 30.43 in | 9.65 in | −0.71% |
| 355/55R15 | 30.37 in | 13.98 in | −0.90% |
| 325/60R15 | 30.35 in | 12.80 in | −0.96% |
| 255/80R15 | 31.06 in | 10.04 in | +1.35% |
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 1.14% height difference is within ±3%, a range often quoted as a rule of thumb; a speedometer calibrated for 265/75R15 reads about 1.1% low.
- 31x10.50R15 is 2 mm (0.07 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 15-inch wheels. Whether a given wheel's width and offset suit 31x10.50R15 has to be checked against the tire maker's approved rim widths and the vehicle.
- Ground clearance under the axles increases by about 0.18 in (half the height difference).
- Sidewall height goes from 7.82 in to 8.00 in. Taller sidewalls generally flex more; ride and handling also depend on the tire's construction and pressure.
Size pages
Frequently asked questions
Is 31x10.50R15 bigger than 265/75R15?
31x10.50R15 is 0.35 in (9 mm, 1.14%) taller than 265/75R15.
Can I replace 265/75R15 with 31x10.50R15?
This page can only compare dimensions: the diameter difference is 1.14%, within the ±3% often quoted as a rule of thumb. It cannot tell you whether 31x10.50R15 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 265/75R15 to 31x10.50R15?
It reads low by about 1.13% of the indicated speed: at an indicated 60 mph you are actually doing 60.7 mph (at 100 km/h, 101.1 km/h).
How does 31x10.50R15 change engine RPM?
Example with a 3.73 axle ratio in direct drive at 65 mph: 2659 rpm on 265/75R15 and 2629 rpm on 31x10.50R15. Restoring the original effective gearing would take an axle ratio of about 3.77. 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.