245/70R15 vs 255/65R15
Going from one to the other changes the overall height by -1.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/70R15 | 255/65R15 | Change |
|---|---|---|---|
| Overall height | 28.5" | 28.1" | -1.6 % |
| Sidewall | 6.75" | 6.53" | -3.4 % |
| Section width | 245 mm | 255 mm | +4.1 % |
| Circumference | 89.5" | 88.1" | -1.6 % |
| Revs per mile | 708 | 719 | +1.6 % |
| Axle height | 14.25" | 14.03" | -5.8 mm |
| Approved rim width | 7–9" | 7–9.5" | overlap 7–9" |
Both are approved on a rim 7" to 9" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 245/70R15. Fit 255/65R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.2 mph | -0.8 |
| 70 mph | 68.9 mph | -1.1 |
| 90 mph | 88.6 mph | -1.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,841 on the road, so it over-counts by 159. At a true 70 mph the first turns 825 times a minute, the second 839.
What drivers reported
Nobody has filed a complaint naming 245/70R15. 255/65R15 carries 1.