225/50R17 vs 205/50R17
New overall diameter
25.07″
was 25.86″
True speed at an indicated 60
58.2 mph
speedometer reads high
Revolutions per mile
804
was 780 · +24
Switching from 225/50R17 to 205/50R17? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 225/50R17 | 205/50R17 | Change |
|---|---|---|---|
| Overall diameter | 25.86″ | 25.07″ | −0.79″ (−3.0%) |
| Sidewall height | 4.43″ (112.5 mm) | 4.04″ (102.5 mm) | −10.0 mm |
| Tread width | 225 mm | 205 mm | −20 mm |
| Circumference | 81.24″ | 78.76″ | −2.47″ |
| Revs per mile | 780 | 804 | +24 |
| Speedometer error | baseline | −3.0% | reads high |
Diameter overlay
225/50R17 205/50R17
Speedometer check
With 205/50R17 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
24.2 mph actual
35 mph shown
33.9 mph actual
45 mph shown
43.6 mph actual
55 mph shown
53.3 mph actual
65 mph shown
63.0 mph actual
75 mph shown
72.7 mph actual
Common questions
- Will 205/50R17 fit instead of 225/50R17?
- Marginal fit — proceed with care. The 3.0% diameter change is between 3% and 5%. It can work, but expect noticeable speedometer error and check wheel-well clearance, scrub radius and gearing before committing. Your speedometer will read higher than your true speed. Overall diameter goes from 25.86″ to 25.07″, a change of −3.0%. As a rule of thumb, under 3% is safe, 3–5% needs a clearance check, and over 5% is not recommended.
- How far off will my speedometer read on 205/50R17?
- At an indicated 60 mph you would actually be travelling about 58.2 mph — a −3.0% error. The speedometer reads high, so you are going slower than it shows.
- What is the difference in revolutions per mile between 225/50R17 and 205/50R17?
- 225/50R17 turns roughly 780 revolutions per mile; 205/50R17 turns roughly 804. That is a change of +24 revolutions per mile, which is what shifts odometer and speedometer readings.