Tire size comparison
275/70R17 vs 285/70R17
285/70R17 is +1.7% taller than 275/70R17: 32.7 in vs 32.2 in (+0.55 in), and 0.4 in wider. With 285/70R17 on a vehicle set up for 275/70R17, 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 (285/70R17 instead of 275/70R17) · 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
275/70R17 vs 285/70R17: full comparison
| 275/70R17 | 285/70R17 | Difference | |
|---|---|---|---|
| Overall diameter | 32.16 in | 32.71 in | +0.55 in (+1.7%) |
| Width | 10.83 in | 11.22 in | +0.39 in (+3.6%) |
| Sidewall height | 7.58 in | 7.85 in | +0.28 in |
| Circumference | 101.0 in | 102.8 in | +1.7 in |
| Revs per mile (nominal) | 627 | 617 | −11 |
| Wheel diameter | 17 in | 17 in | ±0 in |
| Diameter in mm | 817 | 831 | +14 mm |
Speedometer difference
Your speedometer is calibrated for 275/70R17. Fitted with 285/70R17, the actual speed is the reading × 32.71 ÷ 32.16.
| 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 | 55.9 mph | +0.9 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
275/70R17: 32.1–32.2 in published by 4 makers; 285/70R17: 32.7–33.15 in published by 6 makers. Calculated figures assume a nominal tire; the exact difference between two specific tires depends on their models.
More about each size: 275/70R17 · 285/70R17
Related comparisons
FAQ
Which is bigger, 275/70R17 or 285/70R17?
285/70R17 is +1.7% taller than 275/70R17: 32.7 in vs 32.2 in (+0.55 in).
How much will my speedometer be off with 285/70R17 instead of 275/70R17?
The speedometer is calibrated for 275/70R17. With 285/70R17 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 275/70R17 with 285/70R17?
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.