285/35R17 vs 265/35R17
Going from one to the other changes the overall height by -2.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/35R17 | 265/35R17 | Change |
|---|---|---|---|
| Overall height | 24.9" | 24.3" | -2.2 % |
| Sidewall | 3.93" | 3.65" | -7.0 % |
| Section width | 285 mm | 265 mm | -7.0 % |
| Circumference | 78.1" | 76.4" | -2.2 % |
| Revs per mile | 811 | 830 | +2.2 % |
| Axle height | 12.43" | 12.15" | -7.0 mm |
| Approved rim width | 8–10.5" | 7.5–9.5" | overlap 8–9.5" |
Both are approved on a rim 8" 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 285/35R17. Fit 265/35R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 88.0 mph | -2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,778 on the road, so it over-counts by 222. At a true 70 mph the first turns 947 times a minute, the second 968.