245/40R19 vs 235/50R19
New overall diameter
28.25″
was 26.72″
True speed at an indicated 60
63.4 mph
speedometer reads low
Revolutions per mile
714
was 755 · −41
Switching from 245/40R19 to 235/50R19? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 245/40R19 | 235/50R19 | Change |
|---|---|---|---|
| Overall diameter | 26.72″ | 28.25″ | +1.54″ (+5.7%) |
| Sidewall height | 3.86″ (98.0 mm) | 4.63″ (117.5 mm) | +19.5 mm |
| Tread width | 245 mm | 235 mm | −10 mm |
| Circumference | 83.93″ | 88.76″ | +4.82″ |
| Revs per mile | 755 | 714 | −41 |
| Speedometer error | baseline | +5.7% | reads low |
Diameter overlay
245/40R19 235/50R19
Speedometer check
With 235/50R19 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
26.4 mph actual
35 mph shown
37.0 mph actual
45 mph shown
47.6 mph actual
55 mph shown
58.2 mph actual
65 mph shown
68.7 mph actual
75 mph shown
79.3 mph actual
Common questions
- Will 235/50R19 fit instead of 245/40R19?
- Not recommended. A 5.7% 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 26.72″ to 28.25″, a change of +5.7%. 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 235/50R19?
- At an indicated 60 mph you would actually be travelling about 63.4 mph — a +5.7% 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 235/50R19?
- 245/40R19 turns roughly 755 revolutions per mile; 235/50R19 turns roughly 714. That is a change of −41 revolutions per mile, which is what shifts odometer and speedometer readings.