195/55R15 vs 175/65R15
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 | 195/55R15 | 175/65R15 | Change |
|---|---|---|---|
| Overall height | 23.4" | 24.0" | +2.2 % |
| Sidewall | 4.22" | 4.48" | +6.1 % |
| Section width | 195 mm | 175 mm | -10.3 % |
| Circumference | 73.7" | 75.3" | +2.2 % |
| Revs per mile | 860 | 842 | -2.2 % |
| Axle height | 11.72" | 11.98" | +6.5 mm |
| Approved rim width | 5.5–7" | 5–6" | 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 195/55R15. Fit 175/65R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.5 mph | +1.5 |
| 90 mph | 92.0 mph | +2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,218 on the road, so it under-counts by 218. At a true 70 mph the first turns 1004 times a minute, the second 982.