245/40R19 vs 235/55R19
New overall diameter
29.18″
was 26.72″
True speed at an indicated 60
65.5 mph
your speedo reads low
Revolutions per mile
691
was 755, −64
| Measurement | 245/40R19 | 235/55R19 | Change |
|---|---|---|---|
| Overall diameter | 26.72″ | 29.18″ | +2.46″ (+9.2%) |
| Sidewall height | 3.86″ (98.0 mm) | 5.09″ (129.3 mm) | +31.3 mm |
| Tread width | 245 mm | 235 mm | −10 mm |
| Circumference | 83.93″ | 91.66″ | +7.73″ |
| Revs per mile | 755 | 691 | −64 |
| Speedometer error | baseline | +9.2% | reads low |
Diameter overlay
245/40R19 235/55R19
Speedometer check
With 235/55R19 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
27.3 mph actual
35 mph shown
38.2 mph actual
45 mph shown
49.1 mph actual
55 mph shown
60.1 mph actual
65 mph shown
71.0 mph actual
75 mph shown
81.9 mph actual
Common questions
- Will 235/55R19 fit instead of 245/40R19?
- 9.2% 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 26.72″ to 29.18″, a change of +9.2%. 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 235/55R19?
- At an indicated 60 mph you are really doing about 65.5 mph, a +9.2% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 245/40R19 and 235/55R19?
- 245/40R19 turns about 755 times per mile and 235/55R19 turns about 691, a difference of −64. Your speedometer and odometer both count rotations, so this number is what throws them off.