205/55R16 vs 245/70R16
New overall diameter
29.50″
was 24.88″
True speed at an indicated 60
71.2 mph
your speedo reads low
Revolutions per mile
684
was 811, −127
| 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?
- 18.6% is past the 5% mark, which is where this stops being a tire choice and starts being a project. Expect rubbing, meaningful speedometer error, and extra load on ABS, stability control and the drivetrain. Recalibration is the usual fix. Your speedometer will read low, so you are going faster than it says. Overall diameter goes from 24.88″ to 29.50″, a change of +18.6%. The rule of thumb most shops use: under 3% is fine, 3 to 5% needs a clearance check, over 5% needs recalibration.
- How far off will my speedometer read on 245/70R16?
- At an indicated 60 mph you are really doing 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 about 811 times per mile and 245/70R16 turns about 684, a difference of −127. Your speedometer and odometer both count rotations, so this number is what throws them off.