175/65R15 vs 175/65R14
New overall diameter
22.96″
was 23.96″
True speed at an indicated 60
57.5 mph
your speedo reads high
Revolutions per mile
879
was 842, +37
| Measurement | 175/65R15 | 175/65R14 | Change |
|---|---|---|---|
| Overall diameter | 23.96″ | 22.96″ | −1.00″ (−4.2%) |
| Sidewall height | 4.48″ (113.8 mm) | 4.48″ (113.8 mm) | +0.0 mm |
| Tread width | 175 mm | 175 mm | +0 mm |
| Circumference | 75.26″ | 72.12″ | −3.14″ |
| Revs per mile | 842 | 879 | +37 |
| Speedometer error | baseline | −4.2% | reads high |
Diameter overlay
175/65R15 175/65R14
Speedometer check
With 175/65R14 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
24.0 mph actual
35 mph shown
33.5 mph actual
45 mph shown
43.1 mph actual
55 mph shown
52.7 mph actual
65 mph shown
62.3 mph actual
75 mph shown
71.9 mph actual
Common questions
- Will 175/65R14 fit instead of 175/65R15?
- At 4.2% this lands between the 3% and 5% marks. Plenty of people run swaps like this, but you will see real speedometer error, and you want to check the wheel well at full lock and full compression before you buy. Your speedometer will read high, so you are going slower than it says. Overall diameter goes from 23.96″ to 22.96″, a change of −4.2%. 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 175/65R14?
- At an indicated 60 mph you are really doing about 57.5 mph, a −4.2% error. The speedometer reads high, so you are going slower than it shows.
- What is the difference in revolutions per mile between 175/65R15 and 175/65R14?
- 175/65R15 turns about 842 times per mile and 175/65R14 turns about 879, a difference of +37. Your speedometer and odometer both count rotations, so this number is what throws them off.