195/75R15 vs 185/80R15
Going from one to the other changes the overall height by +0.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 195/75R15 | 185/80R15 | Change |
|---|---|---|---|
| Overall height | 26.5" | 26.7" | +0.5 % |
| Sidewall | 5.76" | 5.83" | +1.2 % |
| Section width | 195 mm | 185 mm | -5.1 % |
| Circumference | 83.3" | 83.7" | +0.5 % |
| Revs per mile | 761 | 757 | -0.5 % |
| Axle height | 13.26" | 13.33" | +1.8 mm |
| Approved rim width | 5.5–7" | 5–6.5" | 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 195/75R15. Fit 185/80R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.2 mph | +0.2 |
| 50 mph | 50.3 mph | +0.3 |
| 70 mph | 70.4 mph | +0.4 |
| 90 mph | 90.5 mph | +0.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,052 on the road, so it under-counts by 52. At a true 70 mph the first turns 887 times a minute, the second 883.
What drivers reported
195/75R15 carries 2 complaints. Nobody has filed one naming 185/80R15.