315/70R24.5 vs 295/80R24.5
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 | 315/70R24.5 | 295/80R24.5 | Change |
|---|---|---|---|
| Overall height | 41.9" | 43.1" | +2.9 % |
| Sidewall | 8.68" | 9.29" | +7.0 % |
| Section width | 315 mm | 295 mm | -6.3 % |
| Circumference | 131.5" | 135.3" | +2.9 % |
| Revs per mile | 482 | 468 | -2.9 % |
| Axle height | 20.93" | 21.54" | +15.5 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 315/70R24.5. Fit 295/80R24.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.5 mph | +1.5 |
| 70 mph | 72.0 mph | +2.0 |
| 90 mph | 92.6 mph | +2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,292 on the road, so it under-counts by 292. At a true 70 mph the first turns 562 times a minute, the second 546.