295/80R24.5 vs 275/80R24.5
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 | 295/80R24.5 | 275/80R24.5 | Change |
|---|---|---|---|
| Overall height | 43.1" | 41.8" | -2.9 % |
| Sidewall | 9.29" | 8.66" | -6.8 % |
| Section width | 295 mm | 275 mm | -6.8 % |
| Circumference | 135.3" | 131.4" | -2.9 % |
| Revs per mile | 468 | 482 | +2.9 % |
| Axle height | 21.54" | 20.91" | -16.0 mm |
| Approved rim width | 8.5–11" | 7.5–10" | overlap 8.5–10" |
Both are approved on a rim 8.5" to 10" 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 275/80R24.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.5 mph | -1.5 |
| 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 9,708 on the road, so it over-counts by 292. At a true 70 mph the first turns 546 times a minute, the second 563.