205/55R16 vs 245/70R16
New overall diameter
29.50″
was 24.88″
True speed at an indicated 60
71.2 mph
speedometer reads low
Revolutions per mile
684
was 811 · −127
Switching from 205/55R16 to 245/70R16? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 205/55R16 | 245/70R16 | Change |
|---|---|---|---|
| Overall diameter | 24.88″ | 29.50″ | +4.63″ (+18.6%) |
| Sidewall height | 4.44″ (112.8 mm) | 6.75″ (171.5 mm) | +58.8 mm |
| Tread width | 205 mm | 245 mm | +40 mm |
| Circumference | 78.16″ | 92.69″ | +14.53″ |
| Revs per mile | 811 | 684 | −127 |
| Speedometer error | baseline | +18.6% | reads low |
Diameter overlay
205/55R16 245/70R16
Speedometer check
With 245/70R16 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
29.6 mph actual
35 mph shown
41.5 mph actual
45 mph shown
53.4 mph actual
55 mph shown
65.2 mph actual
65 mph shown
77.1 mph actual
75 mph shown
88.9 mph actual
Common questions
- Will 245/70R16 fit instead of 205/55R16?
- Not recommended. A 18.6% 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 24.88″ to 29.50″, a change of +18.6%. 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 245/70R16?
- At an indicated 60 mph you would actually be travelling about 71.2 mph — a +18.6% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 205/55R16 and 245/70R16?
- 205/55R16 turns roughly 811 revolutions per mile; 245/70R16 turns roughly 684. That is a change of −127 revolutions per mile, which is what shifts odometer and speedometer readings.