255/70R16 vs 245/75R16
Going from one to the other changes the overall height by +1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/70R16 | 245/75R16 | Change |
|---|---|---|---|
| Overall height | 30.1" | 30.5" | +1.4 % |
| Sidewall | 7.03" | 7.23" | +2.9 % |
| Section width | 255 mm | 245 mm | -3.9 % |
| Circumference | 94.4" | 95.7" | +1.4 % |
| Revs per mile | 671 | 662 | -1.4 % |
| Axle height | 15.03" | 15.23" | +5.3 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 245/75R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 71.0 mph | +1.0 |
| 90 mph | 91.2 mph | +1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,138 on the road, so it under-counts by 138. At a true 70 mph the first turns 783 times a minute, the second 772.
What drivers reported
255/70R16 carries 68 complaints and 1 deaths. 245/75R16 carries 188.