135/65R15 vs 155/60R15
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 | 135/65R15 | 155/60R15 | Change |
|---|---|---|---|
| Overall height | 21.9" | 22.3" | +1.9 % |
| Sidewall | 3.45" | 3.66" | +6.0 % |
| Section width | 135 mm | 155 mm | +14.8 % |
| Circumference | 68.8" | 70.1" | +1.9 % |
| Revs per mile | 921 | 903 | -1.9 % |
| Axle height | 10.95" | 11.16" | +5.3 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 135/65R15. Fit 155/60R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 50.9 mph | +0.9 |
| 70 mph | 71.3 mph | +1.3 |
| 90 mph | 91.7 mph | +1.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,189 on the road, so it under-counts by 189. At a true 70 mph the first turns 1074 times a minute, the second 1054.