215/55R16 vs 185/55R16
New overall diameter
24.01″
was 25.31″
True speed at an indicated 60
56.9 mph
speedometer reads high
Revolutions per mile
840
was 797 · +43
Switching from 215/55R16 to 185/55R16? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 215/55R16 | 185/55R16 | Change |
|---|---|---|---|
| Overall diameter | 25.31″ | 24.01″ | −1.30″ (−5.1%) |
| Sidewall height | 4.66″ (118.3 mm) | 4.01″ (101.8 mm) | −16.5 mm |
| Tread width | 215 mm | 185 mm | −30 mm |
| Circumference | 79.52″ | 75.44″ | −4.08″ |
| Revs per mile | 797 | 840 | +43 |
| Speedometer error | baseline | −5.1% | reads high |
Diameter overlay
215/55R16 185/55R16
Speedometer check
With 185/55R16 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
23.7 mph actual
35 mph shown
33.2 mph actual
45 mph shown
42.7 mph actual
55 mph shown
52.2 mph actual
65 mph shown
61.7 mph actual
75 mph shown
71.2 mph actual
Common questions
- Will 185/55R16 fit instead of 215/55R16?
- 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 higher than your true speed. Overall diameter goes from 25.31″ to 24.01″, 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 185/55R16?
- At an indicated 60 mph you would actually be travelling about 56.9 mph — a −5.1% error. The speedometer reads high, so you are going slower than it shows.
- What is the difference in revolutions per mile between 215/55R16 and 185/55R16?
- 215/55R16 turns roughly 797 revolutions per mile; 185/55R16 turns roughly 840. That is a change of +43 revolutions per mile, which is what shifts odometer and speedometer readings.