185/80R15 vs 195/80R15
Going from one to the other changes the overall height by +2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 185/80R15 | 195/80R15 | Change |
|---|---|---|---|
| Overall height | 26.7" | 27.3" | +2.4 % |
| Sidewall | 5.83" | 6.14" | +5.4 % |
| Section width | 185 mm | 195 mm | +5.4 % |
| Circumference | 83.7" | 85.7" | +2.4 % |
| Revs per mile | 757 | 739 | -2.4 % |
| Axle height | 13.33" | 13.64" | +8.0 mm |
| Approved rim width | 5–6.5" | 5.5–7" | 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 185/80R15. Fit 195/80R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,236 on the road, so it under-counts by 236. At a true 70 mph the first turns 883 times a minute, the second 862.