215/80R15 vs 205/80R15
Going from one to the other changes the overall height by -2.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/80R15 | 205/80R15 | Change |
|---|---|---|---|
| Overall height | 28.5" | 27.9" | -2.2 % |
| Sidewall | 6.77" | 6.46" | -4.7 % |
| Section width | 215 mm | 205 mm | -4.7 % |
| Circumference | 89.7" | 87.7" | -2.2 % |
| Revs per mile | 707 | 723 | +2.2 % |
| Axle height | 14.27" | 13.96" | -8.0 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 215/80R15. Fit 205/80R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.5 mph | -1.5 |
| 90 mph | 88.0 mph | -2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,779 on the road, so it over-counts by 221. At a true 70 mph the first turns 824 times a minute, the second 843.