Tire size comparison
265/75R16 vs 31x10.50R15
31x10.50R15 is −2.1% shorter than 265/75R16: 31.0 in vs 31.6 in (−0.65 in), and 0.1 in wider. With 31x10.50R15 on a vehicle set up for 265/75R16, the speedometer shows 60 mph at an actual 58.8 mph. That is within the ±3% difference many shops use as a rule of thumb (not a manufacturer or legal limit).
Set up for: checking a replacement size (31x10.50R15 instead of 265/75R16) · Different situation?
Your current size
e.g. 265/70R17, 2657017 or 33x12.50R20
Where do I find my size?
It's on the tire sidewall, e.g. P265/70R17 115T, and on the tire placard sticker on the driver's door jamb (also in the owner's manual). The placard shows the size the vehicle came with; the sidewall shows what is fitted now. If they differ, use the placard as your starting point. Digits are enough here: 2657017 or 33125020.
Size you're considering
265/75R16 vs 31x10.50R15: full comparison
| 265/75R16 | 31x10.50R15 | Difference | |
|---|---|---|---|
| Overall diameter | 31.65 in | 31.00 in | −0.65 in (−2.1%) |
| Width | 10.43 in | 10.50 in | +0.07 in (+0.6%) |
| Sidewall height | 7.82 in | 8.00 in | +0.18 in |
| Circumference | 99.4 in | 97.4 in | −2.0 in |
| Revs per mile (nominal) | 637 | 651 | +13 |
| Wheel diameter | 16 in | 15 in | −1 in |
| Diameter in mm | 804 | 787 | −16 mm |
Speedometer difference
Your speedometer is calibrated for 265/75R16. Fitted with 31x10.50R15, the actual speed is the reading × 31.00 ÷ 31.65.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 19.6 mph | −0.4 mph |
| 30 mph | 29.4 mph | −0.6 mph |
| 45 mph | 44.1 mph | −0.9 mph |
| 55 mph | 53.9 mph | −1.1 mph |
| 60 mph | 58.8 mph | −1.2 mph |
| 70 mph | 68.6 mph | −1.4 mph |
| 80 mph | 78.4 mph | −1.6 mph |
Real tires: published diameters
265/75R16: 31.5–32 in published by 6 makers; 31x10.50R15: 30.5–31.1 in published by 4 makers. Calculated figures assume a nominal tire; the exact difference between two specific tires depends on their models.
More about each size: 265/75R16 · 31x10.50R15
Related comparisons
FAQ
Which is bigger, 265/75R16 or 31x10.50R15?
31x10.50R15 is −2.1% shorter than 265/75R16: 31.0 in vs 31.6 in (−0.65 in).
How much will my speedometer be off with 31x10.50R15 instead of 265/75R16?
The speedometer is calibrated for 265/75R16. With 31x10.50R15 it shows 60 mph when you are doing 58.8 mph, and 70 mph at 68.6 mph (−2.1%). Your speedometer also has its own factory tolerance.
Can I replace 265/75R16 with 31x10.50R15?
The diameter difference is −2.1%. Whether it fits depends on things this calculation can't see: wheel width and offset, clearance at full lock and over bumps, load index and speed rating, and your vehicle maker's approval. Check your door-jamb placard and owner's manual and ask a tire professional.