195/55R15 vs 185/60R15
Going from one to the other changes the overall height by +1.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 195/55R15 | 185/60R15 | Change |
|---|---|---|---|
| Overall height | 23.4" | 23.7" | +1.3 % |
| Sidewall | 4.22" | 4.37" | +3.5 % |
| Section width | 195 mm | 185 mm | -5.1 % |
| Circumference | 73.7" | 74.6" | +1.3 % |
| Revs per mile | 860 | 850 | -1.3 % |
| Axle height | 11.72" | 11.87" | +3.8 mm |
| Approved rim width | 5.5–7" | 5–6.5" | overlap 5.5–6.5" |
Both are approved on a rim 5.5" to 6.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 195/55R15. Fit 185/60R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.9 mph | +0.9 |
| 90 mph | 91.1 mph | +1.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,126 on the road, so it under-counts by 126. At a true 70 mph the first turns 1004 times a minute, the second 991.