Tire size comparison
185/55R16 vs 205/50R16
205/50R16 is +0.2% taller than 185/55R16: 24.1 in vs 24.0 in (+0.06 in), and 0.8 in wider. With 205/50R16 on a vehicle set up for 185/55R16, the speedometer shows 60 mph at an actual 60.1 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 (205/50R16 instead of 185/55R16) · 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
185/55R16 vs 205/50R16: full comparison
| 185/55R16 | 205/50R16 | Difference | |
|---|---|---|---|
| Overall diameter | 24.01 in | 24.07 in | +0.06 in (+0.2%) |
| Width | 7.28 in | 8.07 in | +0.79 in (+10.8%) |
| Sidewall height | 4.01 in | 4.04 in | +0.03 in |
| Circumference | 75.4 in | 75.6 in | +0.2 in |
| Revs per mile (nominal) | 840 | 838 | −2 |
| Wheel diameter | 16 in | 16 in | ±0 in |
| Diameter in mm | 610 | 611 | +1 mm |
Speedometer difference
Your speedometer is calibrated for 185/55R16. Fitted with 205/50R16, the actual speed is the reading × 24.07 ÷ 24.01.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.0 mph | ±0.0 mph |
| 30 mph | 30.1 mph | +0.1 mph |
| 45 mph | 45.1 mph | +0.1 mph |
| 55 mph | 55.1 mph | +0.1 mph |
| 60 mph | 60.1 mph | +0.1 mph |
| 70 mph | 70.2 mph | +0.2 mph |
| 80 mph | 80.2 mph | +0.2 mph |
Real tires: published diameters
185/55R16: 23.9–24.2 in published by 4 makers; 205/50R16: 23.9–24.3 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: 185/55R16 · 205/50R16
Related comparisons
FAQ
Which is bigger, 185/55R16 or 205/50R16?
205/50R16 is +0.2% taller than 185/55R16: 24.1 in vs 24.0 in (+0.06 in).
How much will my speedometer be off with 205/50R16 instead of 185/55R16?
The speedometer is calibrated for 185/55R16. With 205/50R16 it shows 60 mph when you are doing 60.1 mph, and 70 mph at 70.2 mph (+0.2%). Your speedometer also has its own factory tolerance.
Can I replace 185/55R16 with 205/50R16?
The diameter difference is +0.2%. 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.