185/60R18 vs 205/50R18
Going from one to the other changes the overall height by -2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 185/60R18 | 205/50R18 | Change |
|---|---|---|---|
| Overall height | 26.7" | 26.1" | -2.5 % |
| Sidewall | 4.37" | 4.04" | -7.7 % |
| Section width | 185 mm | 205 mm | +10.8 % |
| Circumference | 84.0" | 81.9" | -2.5 % |
| Revs per mile | 754 | 774 | +2.5 % |
| Axle height | 13.37" | 13.04" | -8.5 mm |
| Approved rim width | 5–6.5" | 5.5–7.5" | 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 185/60R18. Fit 205/50R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.2 mph | -1.8 |
| 90 mph | 87.7 mph | -2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,750 on the road, so it over-counts by 250. At a true 70 mph the first turns 880 times a minute, the second 903.
What drivers reported
Nobody has filed a complaint naming 185/60R18. 205/50R18 carries 2.