225/45R14 vs 235/45R14
Going from one to the other changes the overall height by +1.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/45R14 | 235/45R14 | Change |
|---|---|---|---|
| Overall height | 22.0" | 22.3" | +1.6 % |
| Sidewall | 3.99" | 4.16" | +4.4 % |
| Section width | 225 mm | 235 mm | +4.4 % |
| Circumference | 69.0" | 70.1" | +1.6 % |
| Revs per mile | 918 | 903 | -1.6 % |
| Axle height | 10.99" | 11.16" | +4.5 mm |
| Approved rim width | 6–8.5" | 6.5–8.5" | 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 225/45R14. Fit 235/45R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.8 mph | +0.8 |
| 70 mph | 71.1 mph | +1.1 |
| 90 mph | 91.5 mph | +1.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,161 on the road, so it under-counts by 161. At a true 70 mph the first turns 1071 times a minute, the second 1054.