235/45R14 vs 225/50R14
Going from one to the other changes the overall height by +2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/45R14 | 225/50R14 | Change |
|---|---|---|---|
| Overall height | 22.3" | 22.9" | +2.4 % |
| Sidewall | 4.16" | 4.43" | +6.4 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 70.1" | 71.8" | +2.4 % |
| Revs per mile | 903 | 882 | -2.4 % |
| Axle height | 11.16" | 11.43" | +6.8 mm |
| Approved rim width | 6.5–8.5" | 6–8.5" | overlap 6.5–8.5" |
Both are approved on a rim 6.5" to 8.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 235/45R14. Fit 225/50R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,238 on the road, so it under-counts by 238. At a true 70 mph the first turns 1054 times a minute, the second 1029.