245/35R16 vs 235/40R16
Going from one to the other changes the overall height by +2.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/35R16 | 235/40R16 | Change |
|---|---|---|---|
| Overall height | 22.8" | 23.4" | +2.9 % |
| Sidewall | 3.38" | 3.70" | +9.6 % |
| Section width | 245 mm | 235 mm | -4.1 % |
| Circumference | 71.5" | 73.5" | +2.9 % |
| Revs per mile | 886 | 862 | -2.9 % |
| Axle height | 11.38" | 11.70" | +8.3 mm |
| Approved rim width | 7–9" | 6.5–8.5" | 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 245/35R16. Fit 235/40R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.4 mph | +1.4 |
| 70 mph | 72.0 mph | +2.0 |
| 90 mph | 92.6 mph | +2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,286 on the road, so it under-counts by 286. At a true 70 mph the first turns 1034 times a minute, the second 1005.