315/40R17 vs 295/40R17
Going from one to the other changes the overall height by -2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 315/40R17 | 295/40R17 | Change |
|---|---|---|---|
| Overall height | 26.9" | 26.3" | -2.3 % |
| Sidewall | 4.96" | 4.65" | -6.3 % |
| Section width | 315 mm | 295 mm | -6.3 % |
| Circumference | 84.6" | 82.6" | -2.3 % |
| Revs per mile | 749 | 767 | +2.3 % |
| Axle height | 13.46" | 13.15" | -8.0 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 315/40R17. Fit 295/40R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 87.9 mph | -2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,766 on the road, so it over-counts by 234. At a true 70 mph the first turns 874 times a minute, the second 895.