235/55R19 vs 245/45R19
New overall diameter
27.68″
was 29.18″
True speed at an indicated 60
56.9 mph
your speedo reads high
Revolutions per mile
729
was 691, +37
| Measurement | 235/55R19 | 245/45R19 | Change |
|---|---|---|---|
| Overall diameter | 29.18″ | 27.68″ | −1.50″ (−5.1%) |
| Sidewall height | 5.09″ (129.3 mm) | 4.34″ (110.3 mm) | −19.0 mm |
| Tread width | 235 mm | 245 mm | +10 mm |
| Circumference | 91.66″ | 86.96″ | −4.70″ |
| Revs per mile | 691 | 729 | +37 |
| Speedometer error | baseline | −5.1% | reads high |
Diameter overlay
235/55R19 245/45R19
Speedometer check
With 245/45R19 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 245/45R19 fit instead of 235/55R19?
- 5.1% 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 high, so you are going slower than it says. Overall diameter goes from 29.18″ to 27.68″, a change of −5.1%. 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 245/45R19?
- At an indicated 60 mph you are really doing 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 235/55R19 and 245/45R19?
- 235/55R19 turns about 691 times per mile and 245/45R19 turns about 729, a difference of +37. Your speedometer and odometer both count rotations, so this number is what throws them off.