315/75R24.5 vs 295/80R24.5
Going from one to the other changes the overall height by -0.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 315/75R24.5 | 295/80R24.5 | Change |
|---|---|---|---|
| Overall height | 43.1" | 43.1" | -0.0 % |
| Sidewall | 9.30" | 9.29" | -0.1 % |
| Section width | 315 mm | 295 mm | -6.3 % |
| Circumference | 135.4" | 135.3" | -0.0 % |
| Revs per mile | 468 | 468 | +0.0 % |
| Axle height | 21.55" | 21.54" | -0.3 mm |
| Approved rim width | 8.5–11.5" | 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 315/75R24.5. Fit 295/80R24.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.0 mph | -0.0 |
| 50 mph | 50.0 mph | -0.0 |
| 70 mph | 70.0 mph | -0.0 |
| 90 mph | 90.0 mph | -0.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,995 on the road, so it over-counts by 5. At a true 70 mph the first turns 546 times a minute, the second 546.