235/35R19 vs 255/30R19
Going from one to the other changes the overall height by -1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/35R19 | 255/30R19 | Change |
|---|---|---|---|
| Overall height | 25.5" | 25.0" | -1.8 % |
| Sidewall | 3.24" | 3.01" | -7.0 % |
| Section width | 235 mm | 255 mm | +8.5 % |
| Circumference | 80.0" | 78.6" | -1.8 % |
| Revs per mile | 792 | 806 | +1.8 % |
| Axle height | 12.74" | 12.51" | -5.8 mm |
| Approved rim width | 6.5–8.5" | 7–9.5" | 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 235/35R19. Fit 255/30R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.1 mph | -0.9 |
| 70 mph | 68.8 mph | -1.2 |
| 90 mph | 88.4 mph | -1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,822 on the road, so it over-counts by 178. At a true 70 mph the first turns 924 times a minute, the second 940.
What drivers reported
235/35R19 carries 6 complaints. Nobody has filed one naming 255/30R19.