215/60R18 vs 205/65R18
Going from one to the other changes the overall height by +1.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/60R18 | 205/65R18 | Change |
|---|---|---|---|
| Overall height | 28.2" | 28.5" | +1.2 % |
| Sidewall | 5.08" | 5.25" | +3.3 % |
| Section width | 215 mm | 205 mm | -4.7 % |
| Circumference | 88.5" | 89.5" | +1.2 % |
| Revs per mile | 716 | 708 | -1.2 % |
| Axle height | 14.08" | 14.25" | +4.3 mm |
| Approved rim width | 6–8" | 5.5–7.5" | overlap 6–7.5" |
Both are approved on a rim 6" to 7.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 215/60R18. Fit 205/65R18 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 | 70.8 mph | +0.8 |
| 90 mph | 91.1 mph | +1.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,119 on the road, so it under-counts by 119. At a true 70 mph the first turns 836 times a minute, the second 826.