185/60R15 vs 175/65R15
New overall diameter
23.96″
was 23.74″
True speed at an indicated 60
60.5 mph
your speedo reads low
Revolutions per mile
842
was 850, −8
| Measurement | 185/60R15 | 175/65R15 | Change |
|---|---|---|---|
| Overall diameter | 23.74″ | 23.96″ | +0.22″ (+0.9%) |
| Sidewall height | 4.37″ (111.0 mm) | 4.48″ (113.8 mm) | +2.8 mm |
| Tread width | 185 mm | 175 mm | −10 mm |
| Circumference | 74.58″ | 75.26″ | +0.68″ |
| Revs per mile | 850 | 842 | −8 |
| Speedometer error | baseline | +0.9% | reads low |
Diameter overlay
185/60R15 175/65R15
Speedometer check
With 175/65R15 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
25.2 mph actual
35 mph shown
35.3 mph actual
45 mph shown
45.4 mph actual
55 mph shown
55.5 mph actual
65 mph shown
65.6 mph actual
75 mph shown
75.7 mph actual
Common questions
- Will 175/65R15 fit instead of 185/60R15?
- Overall diameter changes 0.9%; section width changes -10 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 23.74″ to 23.96″, a change of +0.9%. 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 175/65R15?
- At an indicated 60 mph you are really doing about 60.5 mph, a +0.9% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 185/60R15 and 175/65R15?
- 185/60R15 turns about 850 times per mile and 175/65R15 turns about 842, a difference of −8. Your speedometer and odometer both count rotations, so this number is what throws them off.