This is a modification rather than a substitution. Check clearance at full steering lock and full suspension compression, confirm the load rating meets the placard, and expect the speedometer to read low by about 3.2% unless it can be recalibrated for the new size.
Want to try other sizes against these? Open this comparison in the interactive tool.
This is a plus-size: bigger wheel, shorter sidewall
Going from 31X10.50R15 to 32X11.50R17 moves the rim from 15 inches to 17 and drops the aspect ratio from 76 to 65. That is the classic plus-size pattern, and the intention behind it is usually appearance and steering response rather than clearance.
The sidewall shrinks from 8 inches to 7.5 — 0.5 inches less rubber between the rim and the road. Less sidewall flex sharpens turn-in and makes the steering feel more immediate, which is the point.
The trade is real and worth stating plainly. A shorter sidewall transmits more of the road surface into the cabin, and it leaves the rim far more exposed to pothole damage. Replacement cost also rises, because both the larger wheel and the lower-profile tire are more expensive than what they replace.
31X10.50R15 and 32X11.50R17 measured against each other
Both sizes reduced to the same units. The diameter row is the one that drives everything else on this page — ride height, gearing, speedometer accuracy and odometer readings all follow from it.
| Measurement | 31X10.50R15 | 32X11.50R17 | Difference |
|---|---|---|---|
| Overall diameter | 31" | 32" | +1" (+3.2%) |
| Section width | 10.5" (267 mm) | 11.5" (292 mm) | +1" |
| Sidewall height | 8" | 7.5" | −0.5" |
| Rim diameter | 15" | 17" | +2" |
| Circumference | 97.39" | 100.53" | +3.14" |
| Revolutions per mile | 651 | 630 | −20 |
| Ride height at axle | Baseline | +0.5" | +0.5" |
What the dial shows against how fast you are going
Your speedometer was calibrated to 31X10.50R15, which turns about 651 times per mile. Fit 32X11.50R17 at about 630 revolutions per mile and the same wheel speed now represents a greater road speed than the instrument assumes. The error is 3.2% at every speed, so it grows in absolute terms the faster you go.
| Speedometer reads | You are actually doing | Difference |
|---|---|---|
| 30 mph | 31 mph | +1 mph |
| 45 mph | 46.5 mph | +1.5 mph |
| 60 mph | 61.9 mph | +1.9 mph |
| 75 mph | 77.4 mph | +2.4 mph |
Over distance the same proportion applies to the odometer. Every indicated 1,000 miles on 32X11.50R17 is really about 1032 miles covered — worth knowing on a leased vehicle, where recorded mileage and real mileage drift apart.
What this particular change asks you to check
- Section width grows by 1 inches, so the tire sits closer to the strut and the inner liner on both sides.
- Overall height grows by 1 inches, of which 0.5 inches goes upward into the arch — check at full lock and full compression.
- The rim diameter changes from 15 inches to 17 inches, so this swap needs different wheels as well as different tires.
- Speedometer error of 3.2% — check whether your vehicle supports recalibrating for a new tire size.
- Confirm the load index on 32X11.50R17meets or exceeds the figure on the vehicle's tire placard, particularly if the vehicle tows or carries load.
- On all-wheel-drive and four-wheel-drive vehicles, change all four together — mismatched rolling circumferences load the differentials and transfer case continuously.
31X10.50R15 vs 32X11.50R17 FAQ
Is 32X11.50R17 bigger than 31X10.50R15?+
32X11.50R17 measures 32 inches in overall diameter against 31 inches for 31X10.50R15. That makes it 1 inches taller, a change of +3.2%. It is also 1 inches wider in section width.
Will 32X11.50R17 fit in place of 31X10.50R15?+
The diameter change is +3.2%, which is outside the 3% envelope usually treated as a routine substitution. Treat this as a modification: verify clearance at full steering lock and full suspension compression, confirm the load rating meets the vehicle placard, and expect the speedometer to read incorrectly unless it can be recalibrated.
How much lift does 32X11.50R17 give over 31X10.50R15?+
0.5 inches at the axle — half the diameter difference. The other half of the change goes upward into the wheel arch, which is where fitment problems usually appear.
How far off will my speedometer be?+
The speedometer will read low by about 3.2%. At an indicated 60 mph you would actually be travelling about 61.9 mph, and every indicated 1,000 miles would really be about 1032.
Do I need to regear for 32X11.50R17?+
A +3.2% change shifts the effective gearing noticeably. To restore the original engine speed you would multiply the current axle ratio by 1.032. Whether that is worth doing depends on how the vehicle is used — towing and heavily loaded driving make the case sooner than commuting does.
What is the revolutions-per-mile difference?+
31X10.50R15 turns about 651 times per mile and 32X11.50R17 about 630 — a difference of −20 revolutions. That figure is what the speedometer and odometer are calibrated against, which is why both readings shift.
These are nominal figures. Every number above is calculated from the marked size. Real tires vary from nominal by a few millimetres between manufacturers, and by more as tread wears or pressure changes. Use this to plan and to check a quote — measure the actual tire before committing to a tight fitment.