265/35R17 vs 255/40R17
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 | 265/35R17 | 255/40R17 | Change |
|---|---|---|---|
| Overall height | 24.3" | 25.0" | +3.0 % |
| Sidewall | 3.65" | 4.02" | +10.0 % |
| Section width | 265 mm | 255 mm | -3.8 % |
| Circumference | 76.4" | 78.6" | +3.0 % |
| Revs per mile | 830 | 806 | -3.0 % |
| Axle height | 12.15" | 12.52" | +9.3 mm |
| Approved rim width | 7.5–9.5" | 7–9.5" | overlap 7.5–9.5" |
Both are approved on a rim 7.5" to 9.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 265/35R17. Fit 255/40R17 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 10,300 on the road, so it under-counts by 300. At a true 70 mph the first turns 968 times a minute, the second 940.
What drivers reported
Nobody has filed a complaint naming 265/35R17. 255/40R17 carries 3.