245/50R23 vs 245/55R23
Going from one to the other changes the overall height by +3.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/50R23 | 245/55R23 | Change |
|---|---|---|---|
| Overall height | 32.6" | 33.6" | +3.0 % |
| Sidewall | 4.82" | 5.31" | +10.0 % |
| Section width | 245 mm | 245 mm | 0.0 % |
| Circumference | 102.6" | 105.6" | +3.0 % |
| Revs per mile | 618 | 600 | -3.0 % |
| Axle height | 16.32" | 16.81" | +12.3 mm |
| Approved rim width | 7–9" | 7–9" | overlap 7–9" |
Both are approved on a rim 7" to 9" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 245/50R23. Fit 245/55R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.5 mph | +1.5 |
| 70 mph | 72.1 mph | +2.1 |
| 90 mph | 92.7 mph | +2.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,295 on the road, so it under-counts by 295. At a true 70 mph the first turns 721 times a minute, the second 700.