235/70R16 vs 225/65R16
New overall diameter
27.52″
was 28.95″
True speed at an indicated 60
57.0 mph
speedometer reads high
Revolutions per mile
733
was 697 · +36
Switching from 235/70R16 to 225/65R16? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 235/70R16 | 225/65R16 | Change |
|---|---|---|---|
| Overall diameter | 28.95″ | 27.52″ | −1.44″ (−5.0%) |
| Sidewall height | 6.48″ (164.5 mm) | 5.76″ (146.3 mm) | −18.3 mm |
| Tread width | 235 mm | 225 mm | −10 mm |
| Circumference | 90.96″ | 86.44″ | −4.51″ |
| Revs per mile | 697 | 733 | +36 |
| Speedometer error | baseline | −5.0% | reads high |
Diameter overlay
235/70R16 225/65R16
Speedometer check
With 225/65R16 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
23.8 mph actual
35 mph shown
33.3 mph actual
45 mph shown
42.8 mph actual
55 mph shown
52.3 mph actual
65 mph shown
61.8 mph actual
75 mph shown
71.3 mph actual
Common questions
- Will 225/65R16 fit instead of 235/70R16?
- 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 higher than your true speed. Overall diameter goes from 28.95″ to 27.52″, 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 225/65R16?
- At an indicated 60 mph you would actually be travelling about 57.0 mph — a −5.0% error. The speedometer reads high, so you are going slower than it shows.
- What is the difference in revolutions per mile between 235/70R16 and 225/65R16?
- 235/70R16 turns roughly 697 revolutions per mile; 225/65R16 turns roughly 733. That is a change of +36 revolutions per mile, which is what shifts odometer and speedometer readings.