175/85R15 vs 195/80R15
Going from one to the other changes the overall height by +2.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/85R15 | 195/80R15 | Change |
|---|---|---|---|
| Overall height | 26.7" | 27.3" | +2.1 % |
| Sidewall | 5.86" | 6.14" | +4.9 % |
| Section width | 175 mm | 195 mm | +11.4 % |
| Circumference | 83.9" | 85.7" | +2.1 % |
| Revs per mile | 755 | 739 | -2.1 % |
| Axle height | 13.36" | 13.64" | +7.3 mm |
| Approved rim width | 5–6" | 5.5–7" | overlap 5.5–6" |
Both are approved on a rim 5.5" to 6" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 175/85R15. Fit 195/80R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.5 mph | +1.5 |
| 90 mph | 91.9 mph | +1.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,214 on the road, so it under-counts by 214. At a true 70 mph the first turns 881 times a minute, the second 862.