315/50R23 vs 295/55R23
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 315/50R23 | 295/55R23 | Change |
|---|---|---|---|
| Overall height | 35.4" | 35.8" | +1.1 % |
| Sidewall | 6.20" | 6.39" | +3.0 % |
| Section width | 315 mm | 295 mm | -6.3 % |
| Circumference | 111.2" | 112.4" | +1.1 % |
| Revs per mile | 570 | 564 | -1.1 % |
| Axle height | 17.70" | 17.89" | +4.8 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 295/55R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.7 mph | +0.7 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,106 on the road, so it under-counts by 106. At a true 70 mph the first turns 665 times a minute, the second 658.