235/35R14 vs 225/40R14
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 | 235/35R14 | 225/40R14 | Change |
|---|---|---|---|
| Overall height | 20.5" | 21.1" | +3.0 % |
| Sidewall | 3.24" | 3.54" | +9.4 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 64.3" | 66.2" | +3.0 % |
| Revs per mile | 985 | 956 | -3.0 % |
| Axle height | 10.24" | 10.54" | +7.8 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 235/35R14. Fit 225/40R14 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 10,298 on the road, so it under-counts by 298. At a true 70 mph the first turns 1149 times a minute, the second 1116.