195/55R18 vs 185/60R18
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 195/55R18 | 185/60R18 | Change |
|---|---|---|---|
| Overall height | 26.4" | 26.7" | +1.1 % |
| Sidewall | 4.22" | 4.37" | +3.5 % |
| Section width | 195 mm | 185 mm | -5.1 % |
| Circumference | 83.1" | 84.0" | +1.1 % |
| Revs per mile | 763 | 754 | -1.1 % |
| Axle height | 13.22" | 13.37" | +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 195/55R18. Fit 185/60R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,112 on the road, so it under-counts by 112. At a true 70 mph the first turns 890 times a minute, the second 880.