295/70R24.5 vs 275/70R24.5
Going from one to the other changes the overall height by -2.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 295/70R24.5 | 275/70R24.5 | Change |
|---|---|---|---|
| Overall height | 40.8" | 39.7" | -2.7 % |
| Sidewall | 8.13" | 7.58" | -6.8 % |
| Section width | 295 mm | 275 mm | -6.8 % |
| Circumference | 128.1" | 124.6" | -2.7 % |
| Revs per mile | 495 | 509 | +2.7 % |
| Axle height | 20.38" | 19.83" | -14.0 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 295/70R24.5. Fit 275/70R24.5 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 | 68.1 mph | -1.9 |
| 90 mph | 87.6 mph | -2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,730 on the road, so it over-counts by 270. At a true 70 mph the first turns 577 times a minute, the second 593.