295/75R23 vs 295/70R23
Going from one to the other changes the overall height by -2.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 295/75R23 | 295/70R23 | Change |
|---|---|---|---|
| Overall height | 40.4" | 39.3" | -2.9 % |
| Sidewall | 8.71" | 8.13" | -6.7 % |
| Section width | 295 mm | 295 mm | 0.0 % |
| Circumference | 127.0" | 123.3" | -2.9 % |
| Revs per mile | 499 | 514 | +2.9 % |
| Axle height | 20.21" | 19.63" | -14.7 mm |
| Approved rim width | 8.5–11" | 8.5–11" | overlap 8.5–11" |
Both are approved on a rim 8.5" to 11" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 295/75R23. Fit 295/70R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.4 mph | -2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,713 on the road, so it over-counts by 287. At a true 70 mph the first turns 582 times a minute, the second 599.