Tire size comparison
205/55R17 vs 205/50R17
205/50R17 is −3.1% shorter than 205/55R17: 25.1 in vs 25.9 in (−0.81 in), and the same width. With 205/50R17 on a vehicle set up for 205/55R17, the speedometer shows 60 mph at an actual 58.1 mph. That is more than the ±3% difference many shops use as a rule of thumb, so check carefully before switching.
Set up for: going smaller (205/50R17 instead of 205/55R17) · 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
205/55R17 vs 205/50R17: full comparison
| 205/55R17 | 205/50R17 | Difference | |
|---|---|---|---|
| Overall diameter | 25.88 in | 25.07 in | −0.81 in (−3.1%) |
| Width | 8.07 in | 8.07 in | ±0.00 in (±0.0%) |
| Sidewall height | 4.44 in | 4.04 in | −0.40 in |
| Circumference | 81.3 in | 78.8 in | −2.5 in |
| Revs per mile (nominal) | 779 | 804 | +25 |
| Wheel diameter | 17 in | 17 in | ±0 in |
| Diameter in mm | 657 | 637 | −20 mm |
Speedometer difference
Your speedometer is calibrated for 205/55R17. Fitted with 205/50R17, the actual speed is the reading × 25.07 ÷ 25.88.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 19.4 mph | −0.6 mph |
| 30 mph | 29.1 mph | −0.9 mph |
| 45 mph | 43.6 mph | −1.4 mph |
| 55 mph | 53.3 mph | −1.7 mph |
| 60 mph | 58.1 mph | −1.9 mph |
| 70 mph | 67.8 mph | −2.2 mph |
| 80 mph | 77.5 mph | −2.5 mph |
Real tires: published diameters
205/55R17: 25.7–26.2 in published by 3 makers; 205/50R17: 24.9–25.4 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: 205/55R17 · 205/50R17
Related comparisons
FAQ
Which is bigger, 205/55R17 or 205/50R17?
205/50R17 is −3.1% shorter than 205/55R17: 25.1 in vs 25.9 in (−0.81 in).
How much will my speedometer be off with 205/50R17 instead of 205/55R17?
The speedometer is calibrated for 205/55R17. With 205/50R17 it shows 60 mph when you are doing 58.1 mph, and 70 mph at 67.8 mph (−3.1%). Your speedometer also has its own factory tolerance.
Can I replace 205/55R17 with 205/50R17?
The diameter difference is −3.1%. 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.