215/55R17 vs 235/45R17
New overall diameter
25.33″
was 26.31″
True speed at an indicated 60
57.8 mph
your speedo reads high
Revolutions per mile
796
was 767, +30
| Measurement | 215/55R17 | 235/45R17 | Change |
|---|---|---|---|
| Overall diameter | 26.31″ | 25.33″ | −0.98″ (−3.7%) |
| Sidewall height | 4.66″ (118.3 mm) | 4.16″ (105.8 mm) | −12.5 mm |
| Tread width | 215 mm | 235 mm | +20 mm |
| Circumference | 82.66″ | 79.57″ | −3.09″ |
| Revs per mile | 767 | 796 | +30 |
| Speedometer error | baseline | −3.7% | reads high |
Diameter overlay
215/55R17 235/45R17
Speedometer check
With 235/45R17 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
24.1 mph actual
35 mph shown
33.7 mph actual
45 mph shown
43.3 mph actual
55 mph shown
52.9 mph actual
65 mph shown
62.6 mph actual
75 mph shown
72.2 mph actual
Common questions
- Will 235/45R17 fit instead of 215/55R17?
- Overall diameter changes 3.7%; section width changes 20 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 26.31″ to 25.33″, a change of −3.7%. 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 235/45R17?
- At an indicated 60 mph you are really doing about 57.8 mph, a −3.7% error. The speedometer reads high, so you are going slower than it shows.
- What is the difference in revolutions per mile between 215/55R17 and 235/45R17?
- 215/55R17 turns about 767 times per mile and 235/45R17 turns about 796, a difference of +30. Your speedometer and odometer both count rotations, so this number is what throws them off.