Tire size comparison
245/75R16 vs 31x10.50R15
31x10.50R15 is +1.7% taller than 245/75R16: 31.0 in vs 30.5 in (+0.53 in), and 0.9 in wider. With 31x10.50R15 on a vehicle set up for 245/75R16, the speedometer shows 60 mph at an actual 61.0 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 245/75R16) · 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
245/75R16 vs 31x10.50R15: full comparison
| 245/75R16 | 31x10.50R15 | Difference | |
|---|---|---|---|
| Overall diameter | 30.47 in | 31.00 in | +0.53 in (+1.7%) |
| Width | 9.65 in | 10.50 in | +0.85 in (+8.9%) |
| Sidewall height | 7.23 in | 8.00 in | +0.77 in |
| Circumference | 95.7 in | 97.4 in | +1.7 in |
| Revs per mile (nominal) | 662 | 651 | −11 |
| Wheel diameter | 16 in | 15 in | −1 in |
| Diameter in mm | 774 | 787 | +14 mm |
Speedometer difference
Your speedometer is calibrated for 245/75R16. Fitted with 31x10.50R15, the actual speed is the reading × 31.00 ÷ 30.47.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.3 mph | +0.3 mph |
| 30 mph | 30.5 mph | +0.5 mph |
| 45 mph | 45.8 mph | +0.8 mph |
| 55 mph | 56.0 mph | +1.0 mph |
| 60 mph | 61.0 mph | +1.0 mph |
| 70 mph | 71.2 mph | +1.2 mph |
| 80 mph | 81.4 mph | +1.4 mph |
Real tires: published diameters
245/75R16: 30.3–30.8 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: 245/75R16 · 31x10.50R15
Related comparisons
FAQ
Which is bigger, 245/75R16 or 31x10.50R15?
31x10.50R15 is +1.7% taller than 245/75R16: 31.0 in vs 30.5 in (+0.53 in).
How much will my speedometer be off with 31x10.50R15 instead of 245/75R16?
The speedometer is calibrated for 245/75R16. With 31x10.50R15 it shows 60 mph when you are doing 61.0 mph, and 70 mph at 71.2 mph (+1.7%). Your speedometer also has its own factory tolerance.
Can I replace 245/75R16 with 31x10.50R15?
The diameter difference is +1.7%. 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.