315/50R23 vs 295/50R23
Going from one to the other changes the overall height by -2.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 315/50R23 | 295/50R23 | Change |
|---|---|---|---|
| Overall height | 35.4" | 34.6" | -2.2 % |
| Sidewall | 6.20" | 5.81" | -6.3 % |
| Section width | 315 mm | 295 mm | -6.3 % |
| Circumference | 111.2" | 108.7" | -2.2 % |
| Revs per mile | 570 | 583 | +2.2 % |
| Axle height | 17.70" | 17.31" | -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 315/50R23. Fit 295/50R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 88.0 mph | -2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,778 on the road, so it over-counts by 222. At a true 70 mph the first turns 665 times a minute, the second 680.