255/45R19 vs 265/50R19
New overall diameter
29.43″
was 28.04″
True speed at an indicated 60
63.0 mph
speedometer reads low
Revolutions per mile
685
was 719 · −34
Switching from 255/45R19 to 265/50R19? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 255/45R19 | 265/50R19 | Change |
|---|---|---|---|
| Overall diameter | 28.04″ | 29.43″ | +1.40″ (+5.0%) |
| Sidewall height | 4.52″ (114.8 mm) | 5.22″ (132.5 mm) | +17.8 mm |
| Tread width | 255 mm | 265 mm | +10 mm |
| Circumference | 88.08″ | 92.47″ | +4.39″ |
| Revs per mile | 719 | 685 | −34 |
| Speedometer error | baseline | +5.0% | reads low |
Diameter overlay
255/45R19 265/50R19
Speedometer check
With 265/50R19 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
26.2 mph actual
35 mph shown
36.7 mph actual
45 mph shown
47.2 mph actual
55 mph shown
57.7 mph actual
65 mph shown
68.2 mph actual
75 mph shown
78.7 mph actual
Common questions
- Will 265/50R19 fit instead of 255/45R19?
- Marginal fit — proceed with care. The 5.0% diameter change is between 3% and 5%. It can work, but expect noticeable speedometer error and check wheel-well clearance, scrub radius and gearing before committing. Your speedometer will read lower than your true speed. Overall diameter goes from 28.04″ to 29.43″, a change of +5.0%. 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 265/50R19?
- At an indicated 60 mph you would actually be travelling about 63.0 mph — a +5.0% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 255/45R19 and 265/50R19?
- 255/45R19 turns roughly 719 revolutions per mile; 265/50R19 turns roughly 685. That is a change of −34 revolutions per mile, which is what shifts odometer and speedometer readings.