175/65R15 vs 185/60R15
Going from one to the other changes the overall height by -0.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/65R15 | 185/60R15 | Change |
|---|---|---|---|
| Overall height | 24.0" | 23.7" | -0.9 % |
| Sidewall | 4.48" | 4.37" | -2.4 % |
| Section width | 175 mm | 185 mm | +5.7 % |
| Circumference | 75.3" | 74.6" | -0.9 % |
| Revs per mile | 842 | 850 | +0.9 % |
| Axle height | 11.98" | 11.87" | -2.8 mm |
| Approved rim width | 5–6" | 5–6.5" | overlap 5–6" |
Both are approved on a rim 5" to 6" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 175/65R15. Fit 185/60R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.4 mph | -0.6 |
| 90 mph | 89.2 mph | -0.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,910 on the road, so it over-counts by 90. At a true 70 mph the first turns 982 times a minute, the second 991.