295/80R24.5 vs 315/70R24.5
Going from one to the other changes the overall height by -2.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 295/80R24.5 | 315/70R24.5 | Change |
|---|---|---|---|
| Overall height | 43.1" | 41.9" | -2.8 % |
| Sidewall | 9.29" | 8.68" | -6.6 % |
| Section width | 295 mm | 315 mm | +6.8 % |
| Circumference | 135.3" | 131.5" | -2.8 % |
| Revs per mile | 468 | 482 | +2.8 % |
| Axle height | 21.54" | 20.93" | -15.5 mm |
| Approved rim width | 8.5–11" | 8.5–11.5" | 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 295/80R24.5. Fit 315/70R24.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.5 mph | -2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,717 on the road, so it over-counts by 283. At a true 70 mph the first turns 546 times a minute, the second 562.