195/65R15 vs 235/75R15
New overall diameter
28.88″
was 24.98″
True speed at an indicated 60
69.4 mph
your speedo reads low
Revolutions per mile
698
was 807, −109
| 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?
- Overall diameter changes 15.6%; section width changes 40 mm. Diameter comparison alone cannot confirm fitment. Verify the vehicle maker's approved rim width, tire load and speed ratings, and clearance at full steering lock and suspension compression. Confirm any possible ABS, traction-control, speedometer, and drivetrain effects with the vehicle maker or a qualified tire professional. Overall diameter goes from 24.98″ to 28.88″, a change of +15.6%. 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 235/75R15?
- At an indicated 60 mph you are really doing 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 about 807 times per mile and 235/75R15 turns about 698, a difference of −109. Your speedometer and odometer both count rotations, so this number is what throws them off.