205/65R15 vs 195/70R15
Going from one to the other changes the overall height by +1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 205/65R15 | 195/70R15 | Change |
|---|---|---|---|
| Overall height | 25.5" | 25.7" | +1.0 % |
| Sidewall | 5.25" | 5.37" | +2.4 % |
| Section width | 205 mm | 195 mm | -4.9 % |
| Circumference | 80.1" | 80.9" | +1.0 % |
| Revs per mile | 791 | 783 | -1.0 % |
| Axle height | 12.75" | 12.87" | +3.3 mm |
| Approved rim width | 5.5–7.5" | 5.5–7" | overlap 5.5–7" |
Both are approved on a rim 5.5" to 7" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 205/65R15. Fit 195/70R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.7 mph | +0.7 |
| 90 mph | 90.9 mph | +0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,100 on the road, so it under-counts by 100. At a true 70 mph the first turns 923 times a minute, the second 914.