215/50R17 vs 225/45R17
New overall diameter
24.97″
was 25.46″
True speed at an indicated 60
58.8 mph
your speedo reads high
Revolutions per mile
808
was 792, +16
| Measurement | 215/50R17 | 225/45R17 | Change |
|---|---|---|---|
| Overall diameter | 25.46″ | 24.97″ | −0.49″ (−1.9%) |
| Sidewall height | 4.23″ (107.5 mm) | 3.99″ (101.3 mm) | −6.3 mm |
| Tread width | 215 mm | 225 mm | +10 mm |
| Circumference | 80.00″ | 78.45″ | −1.55″ |
| Revs per mile | 792 | 808 | +16 |
| Speedometer error | baseline | −1.9% | reads high |
Diameter overlay
215/50R17 225/45R17
Speedometer check
With 225/45R17 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
24.5 mph actual
35 mph shown
34.3 mph actual
45 mph shown
44.1 mph actual
55 mph shown
53.9 mph actual
65 mph shown
63.7 mph actual
75 mph shown
73.6 mph actual
Common questions
- Will 225/45R17 fit instead of 215/50R17?
- Diameter moves 1.9%, comfortably inside the 3% rule. Your speedometer, ABS, traction control and gearing all stay in the range they were calibrated for. Your speedometer will read high, so you are going slower than it says. Overall diameter goes from 25.46″ to 24.97″, a change of −1.9%. 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 225/45R17?
- At an indicated 60 mph you are really doing about 58.8 mph, a −1.9% error. The speedometer reads high, so you are going slower than it shows.
- What is the difference in revolutions per mile between 215/50R17 and 225/45R17?
- 215/50R17 turns about 792 times per mile and 225/45R17 turns about 808, a difference of +16. Your speedometer and odometer both count rotations, so this number is what throws them off.