315/50R17 vs 295/50R17
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 | 315/50R17 | 295/50R17 | Change |
|---|---|---|---|
| Overall height | 29.4" | 28.6" | -2.7 % |
| Sidewall | 6.20" | 5.81" | -6.3 % |
| Section width | 315 mm | 295 mm | -6.3 % |
| Circumference | 92.4" | 89.9" | -2.7 % |
| Revs per mile | 686 | 705 | +2.7 % |
| Axle height | 14.70" | 14.31" | -10.0 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 315/50R17. Fit 295/50R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 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 9,732 on the road, so it over-counts by 268. At a true 70 mph the first turns 800 times a minute, the second 822.