255/70R16 vs 245/70R16
Going from one to the other changes the overall height by -1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/70R16 | 245/70R16 | Change |
|---|---|---|---|
| Overall height | 30.1" | 29.5" | -1.8 % |
| Sidewall | 7.03" | 6.75" | -3.9 % |
| Section width | 255 mm | 245 mm | -3.9 % |
| Circumference | 94.4" | 92.7" | -1.8 % |
| Revs per mile | 671 | 684 | +1.8 % |
| Axle height | 15.03" | 14.75" | -7.0 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 255/70R16. Fit 245/70R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.4 mph | -0.6 |
| 50 mph | 49.1 mph | -0.9 |
| 70 mph | 68.7 mph | -1.3 |
| 90 mph | 88.3 mph | -1.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,817 on the road, so it over-counts by 183. At a true 70 mph the first turns 783 times a minute, the second 798.
What drivers reported
255/70R16 carries 68 complaints and 1 deaths. 245/70R16 carries 74 and 2 deaths.