235/40R22 vs 245/40R22
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 | 235/40R22 | 245/40R22 | Change |
|---|---|---|---|
| Overall height | 29.4" | 29.7" | +1.1 % |
| Sidewall | 3.70" | 3.86" | +4.3 % |
| Section width | 235 mm | 245 mm | +4.3 % |
| Circumference | 92.4" | 93.4" | +1.1 % |
| Revs per mile | 686 | 679 | -1.1 % |
| Axle height | 14.70" | 14.86" | +4.0 mm |
| Approved rim width | 6.5–8.5" | 7–9" | overlap 7–8.5" |
Both are approved on a rim 7" 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 235/40R22. Fit 245/40R22 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 10,107 on the road, so it under-counts by 107. At a true 70 mph the first turns 800 times a minute, the second 792.