245/45R17 vs 205/50R17
New overall diameter
25.07″
was 25.68″
True speed at an indicated 60
58.6 mph
your speedo reads high
Revolutions per mile
804
was 785, +19
| Measurement | 245/45R17 | 205/50R17 | Change |
|---|---|---|---|
| Overall diameter | 25.68″ | 25.07″ | −0.61″ (−2.4%) |
| Sidewall height | 4.34″ (110.3 mm) | 4.04″ (102.5 mm) | −7.8 mm |
| Tread width | 245 mm | 205 mm | −40 mm |
| Circumference | 80.68″ | 78.76″ | −1.92″ |
| Revs per mile | 785 | 804 | +19 |
| Speedometer error | baseline | −2.4% | reads high |
Diameter overlay
245/45R17 205/50R17
Speedometer check
With 205/50R17 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
24.4 mph actual
35 mph shown
34.2 mph actual
45 mph shown
43.9 mph actual
55 mph shown
53.7 mph actual
65 mph shown
63.5 mph actual
75 mph shown
73.2 mph actual
Common questions
- Will 205/50R17 fit instead of 245/45R17?
- Overall diameter changes 2.4%; section width changes -40 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 25.68″ to 25.07″, a change of −2.4%. 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 205/50R17?
- At an indicated 60 mph you are really doing about 58.6 mph, a −2.4% 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 205/50R17?
- 245/45R17 turns about 785 times per mile and 205/50R17 turns about 804, a difference of +19. Your speedometer and odometer both count rotations, so this number is what throws them off.