Tire size comparison
285/75R16 vs 305/70R16
305/70R16 is −0.1% shorter than 285/75R16: 32.8 in vs 32.8 in (−0.02 in), and 0.8 in wider. With 305/70R16 on a vehicle set up for 285/75R16, the speedometer shows 60 mph at an actual 60.0 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 (305/70R16 instead of 285/75R16) · 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
285/75R16 vs 305/70R16: full comparison
| 285/75R16 | 305/70R16 | Difference | |
|---|---|---|---|
| Overall diameter | 32.83 in | 32.81 in | −0.02 in (−0.1%) |
| Width | 11.22 in | 12.01 in | +0.79 in (+7.0%) |
| Sidewall height | 8.42 in | 8.41 in | −0.01 in |
| Circumference | 103.1 in | 103.1 in | −0.1 in |
| Revs per mile (nominal) | 614 | 615 | ±0 |
| Wheel diameter | 16 in | 16 in | ±0 in |
| Diameter in mm | 834 | 833 | ±0 mm |
Speedometer difference
Your speedometer is calibrated for 285/75R16. Fitted with 305/70R16, the actual speed is the reading × 32.81 ÷ 32.83.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.0 mph | ±0.0 mph |
| 30 mph | 30.0 mph | ±0.0 mph |
| 45 mph | 45.0 mph | ±0.0 mph |
| 55 mph | 55.0 mph | ±0.0 mph |
| 60 mph | 60.0 mph | ±0.0 mph |
| 70 mph | 70.0 mph | ±0.0 mph |
| 80 mph | 80.0 mph | ±0.0 mph |
Real tires: published diameters
285/75R16: 32.7–33.2 in published by 5 makers; 305/70R16: 32.79–33.1 in published by 5 makers. Calculated figures assume a nominal tire; the exact difference between two specific tires depends on their models.
More about each size: 285/75R16 · 305/70R16
Related comparisons
FAQ
Which is bigger, 285/75R16 or 305/70R16?
305/70R16 is −0.1% shorter than 285/75R16: 32.8 in vs 32.8 in (−0.02 in).
How much will my speedometer be off with 305/70R16 instead of 285/75R16?
The speedometer is calibrated for 285/75R16. With 305/70R16 it shows 60 mph when you are doing 60.0 mph, and 70 mph at 70.0 mph (−0.1%). Your speedometer also has its own factory tolerance.
Can I replace 285/75R16 with 305/70R16?
The diameter difference is −0.1%. 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.