125/80R16 vs 135/80R16
Going from one to the other changes the overall height by +2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 125/80R16 | 135/80R16 | Change |
|---|---|---|---|
| Overall height | 23.9" | 24.5" | +2.6 % |
| Sidewall | 3.94" | 4.25" | +8.0 % |
| Section width | 125 mm | 135 mm | +8.0 % |
| Circumference | 75.0" | 77.0" | +2.6 % |
| Revs per mile | 845 | 823 | -2.6 % |
| Axle height | 11.94" | 12.25" | +8.0 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 125/80R16. Fit 135/80R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.8 mph | +1.8 |
| 90 mph | 92.4 mph | +2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,264 on the road, so it under-counts by 264. At a true 70 mph the first turns 986 times a minute, the second 960.