255/35R19 vs 235/40R19
Going from one to the other changes the overall height by +1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/35R19 | 235/40R19 | Change |
|---|---|---|---|
| Overall height | 26.0" | 26.4" | +1.4 % |
| Sidewall | 3.51" | 3.70" | +5.3 % |
| Section width | 255 mm | 235 mm | -7.8 % |
| Circumference | 81.8" | 82.9" | +1.4 % |
| Revs per mile | 775 | 764 | -1.4 % |
| Axle height | 13.01" | 13.20" | +4.8 mm |
| Approved rim width | 7–9.5" | 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 255/35R19. Fit 235/40R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 71.0 mph | +1.0 |
| 90 mph | 91.3 mph | +1.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,144 on the road, so it under-counts by 144. At a true 70 mph the first turns 904 times a minute, the second 891.
What drivers reported
255/35R19 carries 11 complaints. Nobody has filed one naming 235/40R19.