245/45R17 vs 215/45R17
New overall diameter
24.62″
was 25.68″
True speed at an indicated 60
57.5 mph
your speedo reads high
Revolutions per mile
819
was 785, +34
| Measurement | 245/45R17 | 215/45R17 | Change |
|---|---|---|---|
| Overall diameter | 25.68″ | 24.62″ | −1.06″ (−4.1%) |
| Sidewall height | 4.34″ (110.3 mm) | 3.81″ (96.8 mm) | −13.5 mm |
| Tread width | 245 mm | 215 mm | −30 mm |
| Circumference | 80.68″ | 77.34″ | −3.34″ |
| Revs per mile | 785 | 819 | +34 |
| Speedometer error | baseline | −4.1% | reads high |
Diameter overlay
245/45R17 215/45R17
Speedometer check
With 215/45R17 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
24.0 mph actual
35 mph shown
33.6 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 215/45R17 fit instead of 245/45R17?
- At 4.1% 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 25.68″ to 24.62″, a change of −4.1%. 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 215/45R17?
- At an indicated 60 mph you are really doing about 57.5 mph, a −4.1% error. The speedometer reads high, so you are going slower than it shows.
- What is the difference in revolutions per mile between 245/45R17 and 215/45R17?
- 245/45R17 turns about 785 times per mile and 215/45R17 turns about 819, a difference of +34. Your speedometer and odometer both count rotations, so this number is what throws them off.