135/80R17 vs 155/75R17
Going from one to the other changes the overall height by +2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 135/80R17 | 155/75R17 | Change |
|---|---|---|---|
| Overall height | 25.5" | 26.2" | +2.5 % |
| Sidewall | 4.25" | 4.58" | +7.6 % |
| Section width | 135 mm | 155 mm | +14.8 % |
| Circumference | 80.1" | 82.2" | +2.5 % |
| Revs per mile | 791 | 771 | -2.5 % |
| Axle height | 12.75" | 13.08" | +8.3 mm |
| Approved rim width | 3.5–5" | 4–5.5" | overlap 4–5" |
Both are approved on a rim 4" to 5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 135/80R17. Fit 155/75R17 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 | 92.3 mph | +2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,255 on the road, so it under-counts by 255. At a true 70 mph the first turns 923 times a minute, the second 900.