195/65R15 vs 235/75R15
New overall diameter
28.88″
was 24.98″
True speed at an indicated 60
69.4 mph
speedometer reads low
Revolutions per mile
698
was 807 · −109
Switching from 195/65R15 to 235/75R15? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 195/65R15 | 235/75R15 | Change |
|---|---|---|---|
| Overall diameter | 24.98″ | 28.88″ | +3.90″ (+15.6%) |
| Sidewall height | 4.99″ (126.8 mm) | 6.94″ (176.3 mm) | +49.5 mm |
| Tread width | 195 mm | 235 mm | +40 mm |
| Circumference | 78.48″ | 90.72″ | +12.24″ |
| Revs per mile | 807 | 698 | −109 |
| Speedometer error | baseline | +15.6% | reads low |
Diameter overlay
195/65R15 235/75R15
Speedometer check
With 235/75R15 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
28.9 mph actual
35 mph shown
40.5 mph actual
45 mph shown
52.0 mph actual
55 mph shown
63.6 mph actual
65 mph shown
75.1 mph actual
75 mph shown
86.7 mph actual
Common questions
- Will 235/75R15 fit instead of 195/65R15?
- Not recommended. A 15.6% 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 24.98″ to 28.88″, a change of +15.6%. 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 235/75R15?
- At an indicated 60 mph you would actually be travelling about 69.4 mph — a +15.6% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 195/65R15 and 235/75R15?
- 195/65R15 turns roughly 807 revolutions per mile; 235/75R15 turns roughly 698. That is a change of −109 revolutions per mile, which is what shifts odometer and speedometer readings.