255/65R16 vs 245/70R16
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 | 255/65R16 | 245/70R16 | Change |
|---|---|---|---|
| Overall height | 29.1" | 29.5" | +1.6 % |
| Sidewall | 6.53" | 6.75" | +3.5 % |
| Section width | 255 mm | 245 mm | -3.9 % |
| Circumference | 91.3" | 92.7" | +1.6 % |
| Revs per mile | 694 | 684 | -1.6 % |
| Axle height | 14.53" | 14.75" | +5.8 mm |
| Approved rim width | 7–9.5" | 7–9" | 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 255/65R16. Fit 245/70R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.8 mph | +0.8 |
| 70 mph | 71.1 mph | +1.1 |
| 90 mph | 91.4 mph | +1.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,156 on the road, so it under-counts by 156. At a true 70 mph the first turns 810 times a minute, the second 798.
What drivers reported
255/65R16 carries 14 complaints. 245/70R16 carries 74 and 2 deaths.