185/60R15 vs 185/55R16
New overall diameter
24.01″
was 23.74″
True speed at an indicated 60
60.7 mph
speedometer reads low
Revolutions per mile
840
was 850 · −10
Switching from 185/60R15 to 185/55R16? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 185/60R15 | 185/55R16 | Change |
|---|---|---|---|
| Overall diameter | 23.74″ | 24.01″ | +0.27″ (+1.1%) |
| Sidewall height | 4.37″ (111.0 mm) | 4.01″ (101.8 mm) | −9.3 mm |
| Tread width | 185 mm | 185 mm | +0 mm |
| Circumference | 74.58″ | 75.44″ | +0.85″ |
| Revs per mile | 850 | 840 | −10 |
| Speedometer error | baseline | +1.1% | reads low |
Diameter overlay
185/60R15 185/55R16
Speedometer check
With 185/55R16 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
25.3 mph actual
35 mph shown
35.4 mph actual
45 mph shown
45.5 mph actual
55 mph shown
55.6 mph actual
65 mph shown
65.7 mph actual
75 mph shown
75.9 mph actual
Common questions
- Will 185/55R16 fit instead of 185/60R15?
- Good fit. Within the 3% rule — overall diameter changes only 1.1%. Speedometer calibration, ABS, traction control and gearing all stay in their intended range. Your speedometer will read lower than your true speed. Overall diameter goes from 23.74″ to 24.01″, a change of +1.1%. 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 60.7 mph — a +1.1% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 185/60R15 and 185/55R16?
- 185/60R15 turns roughly 850 revolutions per mile; 185/55R16 turns roughly 840. That is a change of −10 revolutions per mile, which is what shifts odometer and speedometer readings.