225/50R17 vs 235/55R17
New overall diameter
27.18″
was 25.86″
True speed at an indicated 60
63.1 mph
speedometer reads low
Revolutions per mile
742
was 780 · −38
Switching from 225/50R17 to 235/55R17? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 225/50R17 | 235/55R17 | Change |
|---|---|---|---|
| Overall diameter | 25.86″ | 27.18″ | +1.32″ (+5.1%) |
| Sidewall height | 4.43″ (112.5 mm) | 5.09″ (129.3 mm) | +16.8 mm |
| Tread width | 225 mm | 235 mm | +10 mm |
| Circumference | 81.24″ | 85.38″ | +4.14″ |
| Revs per mile | 780 | 742 | −38 |
| Speedometer error | baseline | +5.1% | reads low |
Diameter overlay
225/50R17 235/55R17
Speedometer check
With 235/55R17 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
26.3 mph actual
35 mph shown
36.8 mph actual
45 mph shown
47.3 mph actual
55 mph shown
57.8 mph actual
65 mph shown
68.3 mph actual
75 mph shown
78.8 mph actual
Common questions
- Will 235/55R17 fit instead of 225/50R17?
- Not recommended. A 5.1% diameter change exceeds the 5% rule. Expect significant speedometer error, potential clearance and rubbing issues, and stress on ABS, stability control and drivetrain components. Your speedometer will read lower than your true speed. Overall diameter goes from 25.86″ to 27.18″, a change of +5.1%. 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 235/55R17?
- At an indicated 60 mph you would actually be travelling about 63.1 mph — a +5.1% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 225/50R17 and 235/55R17?
- 225/50R17 turns roughly 780 revolutions per mile; 235/55R17 turns roughly 742. That is a change of −38 revolutions per mile, which is what shifts odometer and speedometer readings.