125/75R17 vs 135/65R17
Going from one to the other changes the overall height by -1.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 125/75R17 | 135/65R17 | Change |
|---|---|---|---|
| Overall height | 24.4" | 23.9" | -1.9 % |
| Sidewall | 3.69" | 3.45" | -6.4 % |
| Section width | 125 mm | 135 mm | +8.0 % |
| Circumference | 76.6" | 75.1" | -1.9 % |
| Revs per mile | 827 | 844 | +1.9 % |
| Axle height | 12.19" | 11.95" | -6.0 mm |
| Approved rim width | 3.5–4.5" | 3.5–5" | overlap 3.5–4.5" |
Both are approved on a rim 3.5" to 4.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 125/75R17. Fit 135/65R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.4 mph | -0.6 |
| 50 mph | 49.0 mph | -1.0 |
| 70 mph | 68.6 mph | -1.4 |
| 90 mph | 88.3 mph | -1.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,806 on the road, so it over-counts by 194. At a true 70 mph the first turns 965 times a minute, the second 984.