135/65R15 vs 155/55R15
Going from one to the other changes the overall height by -0.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 135/65R15 | 155/55R15 | Change |
|---|---|---|---|
| Overall height | 21.9" | 21.7" | -0.9 % |
| Sidewall | 3.45" | 3.36" | -2.8 % |
| Section width | 135 mm | 155 mm | +14.8 % |
| Circumference | 68.8" | 68.2" | -0.9 % |
| Revs per mile | 921 | 929 | +0.9 % |
| Axle height | 10.95" | 10.86" | -2.5 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 135/65R15. Fit 155/55R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.6 mph | -0.4 |
| 70 mph | 69.4 mph | -0.6 |
| 90 mph | 89.2 mph | -0.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,910 on the road, so it over-counts by 90. At a true 70 mph the first turns 1074 times a minute, the second 1084.